Go from activity to fragment and to another fragment

Go from activity to fragment and to another fragment - android

I am new at android and I can't seem to understand one thing.
I am trying to jump from MainActivity to MainFragment. In it there is a button. When onClickListener is triggered, it should jump to another ResultFragment. But I can't seem to understand how to do it.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.something.MainActivity">
<fragment
android:id="#+id/container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:layout="#layout/fragment_main" />
</RelativeLayout>
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment fragment = new MainFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment, null).commit();
}
}
public class MainFragment extends Fragment {
public MainFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Button button = (Button) rootView.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getContext(), "iskviesta", Toast.LENGTH_SHORT).show();
getFragmentManager().beginTransaction().replace(R.id.container, new ResultFragment()).commit();
}
});
return rootView;
}
}
public class ResultFragment extends Fragment {
public ResultFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_result, container, false);
return rootView;
}
}
What am I doing wrong? The app doesn't even start.
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.something, PID: 14245
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.something/com.something.MainActivity}: android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
Caused by: java.lang.NullPointerException
at java.lang.VMClassLoader.findLoadedClass(Native Method)
at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:742)
at java.lang.ClassLoader.loadClass(ClassLoader.java:362)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at android.support.v4.app.Fragment.isSupportFragmentClass(Fragment.java:459)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:3321)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:120)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:378)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:33)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:777)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:288)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143)
at com.something.MainActivity.onCreate(MainActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

In your xml use a FrameLayout instead of Fragment:
<FrameLayout
android:id="#+id/container"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
Using a fragment tag will not allow you to do fragment transactions on the view.

You should use getSupportFragmentManager() instead of getFragmentManager in your listener :
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getContext(), "iskviesta", Toast.LENGTH_SHORT).show();
getSupportFragmentManager().beginTransaction().replace(R.id.container, new ResultFragment()).commit();
}
});
And remplace your fragment layout with a FrameLayout in your xml code.
Hope this helps.
Sorry for my english.

Related

Fragments in AppCompatActivity

Could I use this extension if I want to use Fragments in my swipe view activity?
public class Overview_Screen extends AppCompatActivity {
My Fragment classes use this one:
public class MessagesFragmentPortrait extends android.support.v4.app.Fragment {
I am asking this because my app keeps crashing...
Here is my main Activity:
public class Overview_Screen extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_overview_screen);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_overview_screen, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
Intent settings_intent = new Intent(this, Settings_Screen.class);
startActivity(settings_intent);
return true;
}
return super.onOptionsItemSelected(item);
}
public static class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int i) {
switch (i) {
case 0:
return new AccountFragmentPortrait();
case 1:
return new FeedFragmentPortrait();
default:
return new MessagesFragmentPortrait();
}
}
#Override
public int getCount() {
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Account";
case 1:
return "Feed";
case 2:
return "Messages";
}
return null;
}
}
}
and here is my stack trace:
FATAL EXCEPTION: main
Process: de.lukas_schroederoutlook.connect, PID: 3364
java.lang.RuntimeException: Unable to start activity ComponentInfo{de.lukas_schroederoutlook.connect/de.lukas_schroederoutlook.connect.Overview_Screen}:
android.view.InflateException: Binary XML file line #41: Binary XML file line #41: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: android.view.InflateException: Binary XML file line #41: Binary XML file line #41: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #41: Error inflating class fragment
Caused by: java.lang.NullPointerException
at java.lang.VMClassLoader.findLoadedClass(Native Method)
at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:742)
at java.lang.ClassLoader.loadClass(ClassLoader.java:362)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at android.support.v4.app.Fragment.isSupportFragmentClass(Fragment.java:469)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2384)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:120)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:378)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:33)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:77)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:777)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143)
at de.lukas_schroederoutlook.connect.Overview_Screen.onCreate(Overview_Screen.java:42)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
And lastly, here is my overview screen xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="de.lukas_schroederoutlook.connect.Overview_Screen">
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="#dimen/appbar_padding_top"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay">
</android.support.v7.widget.Toolbar>
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
<fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/feed_fragment_portrait"/>
<fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/feed_fragment_landscape"/>
And my overview screen fragment xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="de.lukas_schroederoutlook.connect.Overview_Screen$PlaceholderFragment">
<TextView
android:id="#+id/section_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

You need to specify a class attribute in your <fragment> tags.
<fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/feed_fragment_portrait"/>
<fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/feed_fragment_landscape"/>
Add a class="your.packagename.SomeFragment" on both of those (if you actually need both... Typically you have different layout files for landspace and portrait, not have both in one)
It looks like you are using a ViewPager, though, so do you really need the <fragment> tags at all? I think you can remove them.

You need something like this:
<fragment
android:name="de.lukas_schroederoutlook.connect.FeedFragmentPortrait"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/feed_fragment_portrait"/>
Or use
class=
as cricket said.

Data Binding in an Activity with a MapFragment

I would like to use Data Binding Library in one of my projects but I am getting an error in the activity who has a MapFragment. Not using data binding librery the code works perfectly
My xml main_activity file:
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.Toolbar
android:id="#+id/my_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:elevation="4dp"
android:theme="#style/ThemeOverlay.AppCompat.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
<fragment
android:id="#+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.project.activities.MainActivity" />
</RelativeLayout>
</layout>
And the baseActivity related
public abstract class BaseActivity extends AppCompatActivity {
private ActivityMainBinding binding;
private Toolbar toolbar;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, getContentView());
setContentView(getContentView());//Crashes
getPresenter();
configureToolbar();
Log.d(Constans.LOG_TAG,"On create");
}
private void configureToolbar() {
toolbar = binding.myToolbar;
if (toolbar != null) {
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
}
#Override
protected void onStop() {
super.onStop();
Log.d(Constans.LOG_TAG,"On Stop");
}
#Override
protected void onResume() {
super.onResume();
Log.d(Constans.LOG_TAG,"On resume");
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
return super.onCreateOptionsMenu(menu);
}
protected abstract int getContentView();
protected abstract void getPresenter();
}
And the error I get is :
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.project.activities.MainActivity}: android.view.InflateException: Binary XML file line #18: Binary XML file line #18: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.InflateException: Binary XML file line #18: Binary XML file line #18: Error inflating class fragment
at android.view.LayoutInflater.inflate(LayoutInflater.java:539)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
at com.project.activities.MainActivity.BaseActivity.onCreate(BaseActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5461) 
at java.lang.reflect.Method.invoke(Native Method)
The error itself is on onCreate(Bundle savedInstanceState) method on
setContentView(getContentView());
What I am doing wrong?

remove this line
setContentView(getContentView());//Crashes
and pass your layout resource to
binding = DataBindingUtil.setContentView(this, R.id.main_activity);

Your app crashes because you are trying to get the ContentView while it's null.
You will always need to call setContentView in your before trying to call getContentView.
Try:
setContentView(R.id.YOUR_LAYOUT_ID);//Crashes
binding = DataBindingUtil.setContentView(this, getContentView());

Error inflating class fragment when I try to run the app

I get this error when i try to run my android app:
Process: com.example.ronen.sunplantnew, PID: 28608
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ronen.sunplantnew/com.example.ronen.sunplantnew.MainActivity}: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378)
at android.app.Activity.setContentView(Activity.java:2145)
at com.example.ronen.sunplantnew.MainActivity.onCreate(MainActivity.java:17)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
at android.app.ActivityThread.access$800(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.ronen.sunplantnew.HomeScreen.onCreate(HomeScreen.java:59)
at android.support.v4.app.Fragment.performCreate(Fragment.java:1939)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1029)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1226)
at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1328)
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2284)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:111)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:314)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:31)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:504) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:414) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:365) 
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378) 
at android.app.Activity.setContentView(Activity.java:2145) 
at com.example.ronen.sunplantnew.MainActivity.onCreate(MainActivity.java:17) 
at android.app.Activity.performCreate(Activity.java:5990) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
at android.app.ActivityThread.access$800(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
The main activity java file (MainActivity.java)
public class MainActivity extends FragmentActivity implements HomeScreen.OnFragmentInteractionListener, LightTest.OnFragmentInteractionListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public void onFragmentInteraction(Uri uri) {
}
}
the main activity xml file (activity_main.xml)
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/fragment_container"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.ronen.sunplantnew.MainActivity">
<fragment class="com.example.ronen.sunplantnew.HomeScreen"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/home"/>
</RelativeLayout>
HomeScreen java file (HomeScreen.java):
public class HomeScreen extends android.support.v4.app.Fragment {
private Button newTest;
private Button lastTests;
private Button plants;
private Button about;
private OnFragmentInteractionListener mListener;
public HomeScreen() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #return A new instance of fragment HomeScreen.
*/
public static HomeScreen newInstance() {
HomeScreen fragment = new HomeScreen();
Bundle args = new Bundle();
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
newTest=(Button)getActivity().findViewById(R.id.newTest);
lastTests=(Button)getActivity().findViewById(R.id.lastTests);
plants=(Button)getActivity().findViewById(R.id.plants);
about=(Button)getActivity().findViewById(R.id.about);
newTest.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
toLightTest();
}
});
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_home_screen, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
public void toLightTest(){
// Create new fragment and transaction
Fragment newFragment = new LightTest();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
}
}
HomeScreen xml file (fragment_home_screen.xml):
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.ronen.sunplantnew.HomeScreen">
<ImageView
android:layout_width="150dp"
android:layout_height="wrap_content"
android:id="#+id/imageView2"
android:src="#drawable/sun_plant"
android:layout_centerHorizontal="true"
android:layout_gravity="center" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="About"
android:id="#+id/about"
android:layout_alignBottom="#+id/imageView2"
android:layout_centerHorizontal="true"
android:layout_gravity="center_horizontal|bottom" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Last Tests"
android:id="#+id/lastTests"
android:layout_below="#+id/newTest"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_marginTop="41dp"
android:layout_gravity="left|center_vertical" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New LightTest"
android:id="#+id/newTest"
android:layout_alignTop="#+id/imageView2"
android:layout_alignRight="#+id/imageView2"
android:layout_alignEnd="#+id/imageView2"
android:layout_marginTop="45dp"
android:layout_gravity="center_horizontal|top" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Plants Info"
android:id="#+id/plants"
android:layout_alignTop="#+id/lastTests"
android:layout_toLeftOf="#+id/newTest"
android:layout_toStartOf="#+id/newTest"
android:layout_gravity="right|center_vertical" />
What do i need to do to fix this error?

You're trying to find newTest in your Activity, but it's inside HomeScreen.
Try this instead:
HomeScreen.java
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home_screen, container, false);
newTest = (Button)view.findViewById(R.id.newTest);
lastTests = (Button)view.findViewById(R.id.lastTests);
plants = (Button)view.findViewById(R.id.plants);
about=(Button)view.findViewById(R.id.about);
newTest.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
toLightTest();
}
});
return view;
}

Null TextView object in a fragment

I'm working on dynamically setting a text of TextView in a fragment called 'ChallengeFragment' by creating a method that sets the text. Then, I call the method in FragmentActivity class to update the TextView. However, I am getting error that TextView object is null when the method is called. I am not sure why TextView is null.
Here's the logcat message:
16:36:02.437 4072-4072/eie.android.crunch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: eie.android.crunch, PID: 4072
java.lang.RuntimeException: Unable to start activity ComponentInfo{eie.android.crunch/eie.android.crunch.ChallengePage}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at eie.android.crunch.ChallengeFragment.setNameText(ChallengeFragment.java:76)
at eie.android.crunch.ChallengePage.onCreate(ChallengePage.java:50)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Here is the Fragment class (ChallengeFragment.java):
public class ChallengeFragment extends Fragment {
private Activity mActivity;
private TextView nameText;
private Handler handler =new Handler();
public ChallengeFragment() {
}
public void onAttach(Activity activity) {
super.onAttach(activity);
mActivity = activity;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LayoutInflater lf = getActivity().getLayoutInflater();
View v = lf.inflate(R.layout.fragment_challenge, null);
nameText = (TextView) v.findViewById(R.id.user_name_text_view);
....
return v;
}
public void setNameText(String s) {
nameText.setText(s);
}
public TextView getNameText() {
return nameText;
}
}
And this is the code for FragmentActivity that updates the text of TextView (ChallengePage.java):
public class ChallengePage extends FragmentActivity {
private FriendChallengeFragment initialFriendHabit;
private ChallengeFragment friendHabit;
private ChallengeFragment myHabit;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_challenge);
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fm.beginTransaction();
myHabit = new ChallengeFragment();
initialFriendHabit = new FriendChallengeFragment();
myHabit.onAttach(ChallengePage.this);
initialFriendHabit.onAttach(ChallengePage.this);
fragmentTransaction
.replace(R.id.my_habit, myHabit ,"fragment_top")
.replace(R.id.friend_habit, initialFriendHabit, "fragment_bottom")
.commit();
Intent intent = getIntent();
String challengedUsername = intent.getStringExtra("username");
if(challengedUsername != null) {
friendHabit = new ChallengeFragment();
friendHabit.onAttach(ChallengePage.this);
fragmentTransaction.replace(R.id.friend_habit, friendHabit, "fragment_bottom");
friendHabit.setNameText(challengedUsername);
}
}
}
And this is the layout file that contains the fragment (fragment_challenge.xml):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#color/white"
android:id="#+id/user_name_text_view"
android:layout_gravity="center_horizontal"
android:text="User Name"
android:textSize="30dp"
android:layout_marginTop="30dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#color/white"
android:id="#+id/habit_name_text"
android:layout_gravity="center_horizontal"
android:text="Habit Name"
android:textSize="40dp"
android:layout_marginTop="20dp"/>
<ProgressBar
android:layout_height="wrap_content"
android:layout_width="312dp"
style="#android:style/Widget.ProgressBar.Horizontal"
android:id="#+id/progressBar"
android:layout_marginTop="50dp"
android:layout_gravity="center_horizontal"/>
</LinearLayout>
I've looked at other stackoverflow questions relating to this but could not find answers.

The problem is your fragment's setNameText() method is called before onCreateView() has run, so your TextView has not been initialized yet. You have to wait until later to set the name text.
If you always have the name text when you are creating and adding the fragment, then it's better to pass that as an argument to the fragment and have it set the text of the TextView at the appropriate time. Something like this:
public class ChallengeFragment extends Fragment {
public static ChallengeFragment newInstance(String name) {
ChallengeFragment fragment = new ChallengeFragment();
Bundle args = new Bundle();
args.putString("username", name);
fragment.setArguments(args);
return fragment;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
Bundle args = getArguments();
if (args != null) {
String name = args.getString("username");
nameText.setText(name);
}
}
// everything else
}
A few things to note:
Do not create a constructor. Fragments need to have a default (no argument) constructor so that Android can instantiate them. This newInstance pattern is typically regarded as the best practice.
Use onActivityCreated because at that time you know the Activity is created and that the fragment's view hierarchy has been created.
Fragment arguments persist across configuration changes, so you shouldn't need to do anything special for that.
Also, you should not be calling onAttach() yourself, that's a lifecycle method that the OS calls on your fragment.

List View Fragment Won't Display

I am trying to display a list in my main activity using a ListFragment. The list is populated by my custom ArrayAdapter that uses a custom object. I am having trouble getting this list to show in the app. When I debug, it doesn't show any errors but the app immediately crashes.
Here is my fragment
Edit: I have tried several responses and have narrowed down the issue to the momentObjectListView.setAdapter(momentObjectAdapter) in the ListViewFragment. I cannot find a reason why the momentObjectAdapter would be null so it must be momentObjectListView however I cannot find where the issue stems. Any help would be much appreciated. My activity_main.xml, fragment, main activity, and adapter code are all included.
public class ListViewFragment extends ListFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Activity myAct = getActivity();
View view = inflater.inflate(R.layout.activity_main, container, false);
ListView momentObjectListView = (ListView)view.findViewById(R.id.list_item);
//ListView momentObjectListView = getListView();
MomentObjectAdapter momentObjectAdapter = new MomentObjectAdapter(myAct, R.layout.moment_object_list_item);
//momentObjectListView.setAdapter(momentObjectAdapter);
List<MomentObject> myMoments = getMoments();
for(final MomentObject entry : myMoments) {
momentObjectAdapter.add(entry);
}
//ListViewFragment.this.setListAdapter(momentObjectAdapter);
momentObjectListView.setAdapter(momentObjectAdapter);
return view;
}
private List<MomentObject> getMoments() {
// Let's setup some test data.
// Normally this would come from some asynchronous fetch into a data source
// such as a sqlite database, or an HTTP request
final List<MomentObject> entries = new ArrayList<MomentObject>();
for(int i = 1; i < 50; i++) {
entries.add(
new MomentObject(
"Test Entry " + i,
"Anonymous Author",
new GregorianCalendar(2011, 11, i).getTime(),
R.drawable.photoicon
)
);
}
return entries;
}
}
And here is my activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity"
android:background="#ffffffff">
<fragment android:name="com.malatras.moment2.ListViewFragment"
android:id="#+id/list"
android:layout_weight="1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
Please let me know if there is anything I need to provide to solve this.
LogCat:
e02-24 18:54:29.119 2325-2325/com.malatras.moment2 I/art﹕ Not late-enabling -Xcheck:jni (already on)
02-24 18:54:29.191 2325-2325/com.malatras.moment2 D/AndroidRuntime﹕ Shutting down VM
02-24 18:54:29.191 2325-2325/com.malatras.moment2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.malatras.moment2, PID: 2325
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.malatras.moment2/com.malatras.moment2.MainActivity}: android.view.InflateException: Binary XML file line #9: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
at android.app.Activity.setContentView(Activity.java:2144)
at com.malatras.moment2.MainActivity.onCreate(MainActivity.java:11)
at android.app.Activity.performCreate(Activity.java:5933)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.malatras.moment2.ListViewFragment.onCreateView(ListViewFragment.java:34)
at android.app.Fragment.performCreateView(Fragment.java:2053)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1045)
at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1147)
at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2116)
at android.app.Activity.onCreateView(Activity.java:5282)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
            at android.app.Activity.setContentView(Activity.java:2144)
            at com.malatras.moment2.MainActivity.onCreate(MainActivity.java:11)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
MainActivity:
public class MainActivity extends ListActivity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MomentObjectAdapter:
public final class MomentObjectAdapter extends ArrayAdapter<MomentObject> {
private final int momentObjectLayoutResource;
public MomentObjectAdapter(final Context context, final int momentObjectLayoutResource) {
super(context, 0);
this.momentObjectLayoutResource = momentObjectLayoutResource;
}
#Override
public View getView(final int position, final View convertView, final ViewGroup parent) {
// We need to get the best view (re-used if possible) and then
// retrieve its corresponding ViewHolder, which optimizes lookup efficiency
final View view = getWorkingView(convertView);
final ViewHolder viewHolder = getViewHolder(view);
final MomentObject entry = getItem(position);
// Setting the title view is straightforward
viewHolder.titleView.setText(entry.getTitle());
// Setting the subTitle view requires a tiny bit of formatting
final String formattedSubTitle = String.format("By %s on %s",
entry.getAuthor(),
DateFormat.getDateInstance(DateFormat.SHORT).format(entry.getPostDate())
);
viewHolder.subTitleView.setText(formattedSubTitle);
// Setting image view is also simple
viewHolder.imageView.setImageResource(entry.getIcon());
return view;
}
private View getWorkingView(final View convertView) {
// The workingView is basically just the convertView re-used if possible
// or inflated new if not possible
View workingView = null;
if(null == convertView) {
final Context context = getContext();
final LayoutInflater inflater = (LayoutInflater)context.getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
workingView = inflater.inflate(momentObjectLayoutResource, null);
} else {
workingView = convertView;
}
return workingView;
}
private ViewHolder getViewHolder(final View workingView) {
// The viewHolder allows us to avoid re-looking up view references
// Since views are recycled, these references will never change
final Object tag = workingView.getTag();
ViewHolder viewHolder = null;
if(null == tag || !(tag instanceof ViewHolder)) {
viewHolder = new ViewHolder();
viewHolder.titleView = (TextView) workingView.findViewById(R.id.moment_object_title);
viewHolder.subTitleView = (TextView) workingView.findViewById(R.id.moment_object_subtitle);
viewHolder.imageView = (ImageView) workingView.findViewById(R.id.moment_object_icon);
workingView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) tag;
}
return viewHolder;
}
/**
* ViewHolder allows us to avoid re-looking up view references
* Since views are recycled, these references will never change
*/
private static class ViewHolder {
public TextView titleView;
public TextView subTitleView;
public ImageView imageView;
}
}
moment_object_list_item:
<?xml version="1.0" encoding="utf-8"?>
<!-- Layout for individual news entries in a list -->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<!-- Icon shown next to the title/subtitle -->
<ImageView
android:id="#+id/moment_object_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:padding="3dp" />
<!-- Title of the news entry -->
<TextView
android:id="#+id/moment_object_title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_toRightOf="#id/moment_object_icon"
android:layout_alignTop="#id/moment_object_icon"
android:layout_margin="5dp"
android:textSize="14sp"
android:textStyle="bold" />
<!-- Subtitle contains author and date -->
<TextView
android:id="#+id/moment_object_subtitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#id/moment_object_title"
android:layout_below="#id/moment_object_title"
android:textSize="12sp" />
</RelativeLayout>

This code I don't like and not compatible with your method getMoments is:
for(final MomentObject entry : getMoments()) {
momentObjectAdapter.add(entry);
}
For now try this for a quick sample fix:
List<MomentObject> myMoments = getMoments();
for(final MomentObject entry : myMoments) {
The reason is getMoments() in the for loop is evaluated dynamically. I think so even though you declared it with final.
In the log,
Attempt to invoke virtual method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a
null object reference
I believe object momentObjectListView is null. I could not find the UI in fragment_list_view.xml. It is however in activity_main.xml. Sample code :
View view = inflater.inflate(R.layout.activity_main, container, false);
ListView momentObjectListView = (ListView)view.findViewById(R.id.list);
Sample layout element for a ListFragment in activity_main:
<fragment android:name="com.malatras.moment2.ListViewFragment"
android:id="#+id/list"
...>
A good webpage for explaining layouts is required for understanding the basics # Layouts .

Change in your XML file this line : android:id="#+id/list"
to:
android:id="#id/android:list
and in ListViewFragment change this : ListView momentObjectListView =(ListView)view.findViewById(R.id.list);
to this:
ListView momentObjectListView = (ListView)view.findViewById(android.R.id.list);

In your Logcat file, it says
android.view.InflateException: Binary XML file line #9: Error
inflating class fragment
This means an xml file is not proper. Also deeper in the log,
The code MainActivity.onCreate(MainActivity.java:11)
...
Caused by: java.lang.NullPointerException: Attempt to invoke virtual
method 'void
android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a
null object reference at
com.malatras.moment2.ListViewFragment.onCreateView(ListViewFragment.java:34)
...
ListViewFragment.onCreateView(ListViewFragment.java:34)
Need to load file ListViewFragment.java too. In order to save time, perhaps post more files.

Another possible good code change is to modify ListViewFragment definition from:
public class ListViewFragment extends ListFragment {
to:
public class ListViewFragment extends Fragment implements AbsListView.OnItemClickListener {
The OnItemClickListener is optional.
The reason I say this is that MainActivity already hosts ListView object through ListActivity. Another reason, Android Studio wizard generates the "to" suggested code. And it sounds good to me.
Another way is to remove ListActivity from MainActivity to just Activity, with the same reason.
All these suggestions may be considered to be code style however.

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The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

Go from activity to fragment and to another fragment - android

In your xml use a FrameLayout instead of Fragment: <FrameLayout android:id="#+id/container" android:layout_width="wrap_content" android:layout_height="wrap_content" /> Using a fragment tag will not allow you to do fragment transactions on the view.

Related

Fragments in AppCompatActivity

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Error inflating class fragment when I try to run the app

Null TextView object in a fragment

List View Fragment Won't Display

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