New to Android. Not sure how many method I am supposed to upload, so I will upload the just method with the error.
I am following a book Android Application Development for Dummies 3rd edition, but getting an error even though I checked for code discrepancies.
Here is the method.
package com.dan190.tasks.activity;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toolbar;
import com.dan190.tasks.R;
import com.dan190.tasks.fragment.TaskEditFragment;
public class TaskEditActivity extends Activity {
public static final String EXTRA_TASKID = "taskId";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_task_edit);
setActionBar((Toolbar) findViewById(R.id.toolbar));
long id = getIntent().getLongExtra(TaskEditActivity.EXTRA_TASKID, 0L);
Fragment fragment = TaskEditFragment.newInstance(id);
String fragment_tag = TaskEditFragment.DEFAULT_FRAGMENT_TAG;
/** This part below is where the bug happens
** If I comment this part out, app still runs
**/
if (savedInstanceState == null) {
getFragmentManager().beginTransaction().add(
R.id.container,
fragment,
fragment_tag).commit();
}
}
}
Here is the error
07-17 11:52:47.110 29969-29969/com.dan190.tasks E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.dan190.tasks, PID: 29969
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dan190.tasks/com.dan190.tasks.activity.TaskEditActivity}: java.lang.IllegalArgumentException: Target must not be null.
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: java.lang.IllegalArgumentException: Target must not be null.
at com.squareup.picasso.RequestCreator.into(RequestCreator.java:553)
at com.squareup.picasso.RequestCreator.into(RequestCreator.java:536)
at com.dan190.tasks.fragment.TaskEditFragment.onCreate(TaskEditFragment.java:56)
at android.app.Fragment.performCreate(Fragment.java:2031)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:863)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.app.BackStackRecord.run(BackStackRecord.java:833)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1452)
at android.app.Activity.performStart(Activity.java:5952)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)
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)
Thanks
Related
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I'm very new to Android UI, I've been looking for a place I can learn the basic structure of UI and how communication and layouts should work. But regardless. My problem comes from me trying to change the value of a TextView within a fragment. I keep getting a nullPointerException when i try to change the value. I am using a fragment manager to refer to the fragment.
Here's the fragment code:
package com.archronix.infotainment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class Fragment1 extends android.support.v4.app.Fragment {
public TextView status;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_fragment1, container,
false);
return v;
}
public static Fragment1 newInstance() {
Fragment1 f = new Fragment1();
return f;
}
public void postText(String str){
status.setText(status.getText()+"\n"+str);
}
}
And this is how i declare my fragment manager:
fragment1 = (Fragment1)
getSupportFragmentManager().findFragmentById(R.id.fragment1);
And, how I use it:
fragment1.postText("testtext");
My logcat:
05-15 10:56:42.406 4109-4109/com.archronix.infotainment E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.archronix.infotainment, PID: 4109
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.archronix.infotainment/com.archronix.infotainment.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.archronix.infotainment.Fragment1.postText(java.lang.String)' on a null object reference
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: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.archronix.infotainment.Fragment1.postText(java.lang.String)' on a null object reference
at com.archronix.infotainment.MainActivity.onCreate(MainActivity.java:102)
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)
Apologies for my newbieness. I've read 20 stack overflow posts regarding similar topics but all seem to be either outdated or not consistent. What is the best way to accomplish my task? Thank you.
status variable is not assigned to any textview.
Add the following code in onCreateView before return statement
status=v.findViewById(R.id.<nameoftextview>);
In onCreateView you should initialize your TextView like so:
status = (TextView) v.findViewById(R.id.tv_status);
If you know the text that you want to set before the FragmentTransaction you can use a Bundle (How to transfer some data to another Fragment?)
So my code simply makes a list of CardViews using RecyclerView. Upon running my code i kept getting a weird error claiming there was an error in my xml. After tinkering for a while i found out that in my layout file if i change <RecyclerView> to <android.support.v7.widget.RecyclerView> everything would work just fine. Why is this happening? My activity.
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import java.util.ArrayList;
public class CardListActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_card_list);
RecyclerView recyclerView = (RecyclerView)findViewById(R.id.cardList);
recyclerView.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(linearLayoutManager);
ArrayList<String> list = new ArrayList<>();
for(int i = 0; i < 20; i++) {list.add("Item " + i);}
CardListAdapter cardListAdapter = new CardListAdapter(list);
recyclerView.setAdapter(cardListAdapter);
}
}
My Adapter
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.List;
public class CardListAdapter extends RecyclerView.Adapter<CardListAdapter.CardListViewHolder> {
private List<String> list;
public CardListAdapter(List<String> list) {
this.list = list;
}
#Override
public CardListViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_layout,viewGroup,false);
return new CardListViewHolder(v);
}
#Override
public void onBindViewHolder(CardListViewHolder cardListViewHolder, int i) {
String s = list.get(i);
cardListViewHolder.title.setText(s);
}
#Override
public int getItemCount() {
return list.size();
}
public static class CardListViewHolder extends RecyclerView.ViewHolder {
TextView title;
public CardListViewHolder(View itemView) {
super(itemView);
title = (TextView)itemView.findViewById(R.id.title);
}
}
}
My layout file, note, changing <RecyclerView> to <android.support.v7.widget.RecyclerView> fixes the error.
<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=".CardListActivity">
<RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/cardList">
</RecyclerView>
When i run with <RecyclerView> i get this error, .
`Process: com.liquidink.lollipopmaterialui, PID: 7317
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.liquidink.lollipopmaterialui/com.liquidink.lollipopmaterialui.CardListActivity}: android.view.InflateException: Binary XML file line #8: Error inflating class RecyclerView
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 #8: Error inflating class RecyclerView
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:757)
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 android.support.v7.app.ActionBarActivityDelegateBase.setContentView(ActionBarActivityDelegateBase.java:228)
at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:102)
at com.liquidink.lollipopmaterialui.CardListActivity.onCreate(CardListActivity.java:18)
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.ClassNotFoundException: Didn't find class "android.view.RecyclerView" on path: DexPathList[[zip file "/data/app/com.liquidink.lollipopmaterialui-2/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
at android.view.LayoutInflater.createView(LayoutInflater.java:571)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:665)
at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:65)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:682)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:741)
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 android.support.v7.app.ActionBarActivityDelegateBase.setContentView(ActionBarActivityDelegateBase.java:228)
at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:102)
at com.liquidink.lollipopmaterialui.CardListActivity.onCreate(CardListActivity.java:18)
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)
Suppressed: java.lang.ClassNotFoundException: android.view.RecyclerView
at java.lang.Class.classForName(Native Method)
at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
... 26 more
Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available
`
You should add the RecyclerView in the XML in this way:
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/cardList">
</android.support.v7.widget.RecyclerView>
Hope it helps!
RecyclerView is not included in base Android framework, only widgets in base Android framework (like ListView, GridView etc) can be specified in layout without full namespace. RecyclerView is part of recyclerview-v7 support library.
I meet this problem today.
And solved it.
first step:keep the support-libs you used are same version
compile 'com.android.support:appcompat-v7:23.1.1'
compile 'com.android.support:support-v4:23.1.1'
compile 'com.android.support:recyclerview-v7:23.1.1'
second step:you should add recyclerView to your proguard files
-keep class android.support.v7.widget.** {*;}
// I`ve just keep all widgets
Make sure to include before you add RecyclerView to your XML
compile 'com.android.support:recyclerview-v7:22.2.0'
compile 'com.android.support:appcompat-v7:22.2.0'
If you created RecyclerView in your XML before adding these dependencies, to make it work you should remove (comment) your recycler view, build project without it and then add it back. Otherwise it still shows Inflate exception in binary XML line #n.
Check reference in build.gradle
In your layout xml file be, write your RecyclerView component's name as a whole with its package like that android.support.v7.widget.RecyclerViewnot like RecyclerView
now ready to lunch. Good trails
I am trying to make a simple timer using the Timer and TimerTask classes. I keep getting the following error:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
Here is my code:
package com.austinheitmann.stopwatch;
import android.os.CountDownTimer;
import android.os.SystemClock;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import java.util.Timer;
import java.util.TimerTask;
public class MainActivity extends ActionBarActivity {
TextView timerf;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timerf = (TextView) findViewById(R.id.timer);
}
int i=0;
TimerTask time = new TimerTask() {
public void run() {
i++;
int k = i/60;
int j = i%60;
if (j>9) {
timerf.setText("seconds remaining: " + k + ":" + j);
}else {
timerf.setText("seconds remaining: " + k + ":0" + j);
}
Log.d("Uhh", "Sec:" + i);
}
};
Timer timers = new Timer();
public void startB(View view) {
timers.schedule(time, 100000000, 1000);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
}
Here is the xml file(layout):
<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">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="0:00"
android:id="#+id/timer"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="54dp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Start/Pause"
android:id="#+id/start"
android:layout_below="#+id/timer"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="119dp"
android:onClick="startB"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Stop/Reset"
android:id="#+id/stop"
android:layout_alignBottom="#+id/start"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</RelativeLayout>
Every solution I have seen to this error has to do with the layout but I am not altering that in anyway. I have moved to the TimerTask in the startB class also and get the same error. How can I fix this error?
Here's the entire error I get from one run after clearing the logcat (I put ** where the error occurs at):
01-16 12:27:21.008 2455-2455/com.austinheitmann.stopwatch I/art﹕ Not late-enabling -Xcheck:jni (already on)
01-16 12:27:21.119 2455-2455/com.austinheitmann.stopwatch D/AndroidRuntime﹕ Shutting down VM
--------- beginning of crash
01-16 12:27:21.123 2455-2455/com.austinheitmann.stopwatch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.austinheitmann.stopwatch, PID: 2455
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.austinheitmann.stopwatch/com.austinheitmann.stopwatch.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
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 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2071)
at com.austinheitmann.stopwatch.MainActivity.<init>(MainActivity.java:25)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1572)
at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
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)
01-16 12:44:57.778 2582-2582/com.austinheitmann.stopwatch D/AndroidRuntime﹕ Shutting down VM
01-16 12:44:57.778 2582-2582/com.austinheitmann.stopwatch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.austinheitmann.stopwatch, PID: 2582
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.austinheitmann.stopwatch/com.austinheitmann.stopwatch.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
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 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2071)
at com.austinheitmann.stopwatch.MainActivity.<init>(MainActivity.java:25)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1572)
at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
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)
01-16 12:46:25.059 2641-2641/com.austinheitmann.stopwatch D/AndroidRuntime﹕ Shutting down VM
01-16 12:46:25.059 2641-2641/com.austinheitmann.stopwatch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.austinheitmann.stopwatch, PID: 2641
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.austinheitmann.stopwatch/com.austinheitmann.stopwatch.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
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 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2071)
at com.austinheitmann.stopwatch.MainActivity.<init>(MainActivity.java:25)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1572)
at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
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)
01-16 12:47:50.630 2702-2702/com.austinheitmann.stopwatch D/AndroidRuntime﹕ Shutting down VM
01-16 12:47:50.630 2702-2702/com.austinheitmann.stopwatch E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.austinheitmann.stopwatch, PID: 2702
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.austinheitmann.stopwatch/com.austinheitmann.stopwatch.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
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 'android.view.View android.view.Window.findViewById(int)' on a null object reference**
at android.app.Activity.findViewById(Activity.java:2071)
at com.austinheitmann.stopwatch.MainActivity.<init>(MainActivity.java:25)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1572)
at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
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)
You are trying to findViewById before the activity's context is ready.
If you want to access timerf in other methods too, create a class member but make the initialization in the onCreate after setContentView:
TextView timerf;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timerf = (TextView) findViewById(R.id.timer);
}
Update:
I didn't notice the other class member variables you're instantiating. They are referencing timerf which null.
You need to initialize them in the onCreate too. Here's the full code that should work:
package com.austinheitmann.stopwatch;
import android.os.CountDownTimer;
import android.os.SystemClock;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import java.util.Timer;
import java.util.TimerTask;
public class MainActivity extends ActionBarActivity {
Timer timers = new Timer();
TextView timerf;
TimerTask time;
int i=0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timerf = (TextView) findViewById(R.id.timer);
time = new TimerTask() {
public void run() {
i++;
int k = i/60;
int j = i%60;
if (j>9) {
timerf.setText("seconds remaining: " + k + ":" + j);
}else {
timerf.setText("seconds remaining: " + k + ":0" + j);
}
Log.d("Uhh", "Sec:" + i);
}
};
}
public void startB(View view) {
timers.schedule(time, 100000000, 1000);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
First of you use the constructor public MainActivity()and
Timer timer; and long startTime; long stopTime Declare Gobble variable
public MainActivity() {
timer = new Timer();
startTime = System.currentTimeMillis();
stopTime = 0;
}
I'm currently trying to implement Material Design activity transitions. For a reason i really don't know, it crashes. Can someone give me a clue? (I don't know if it's important, but inside my MainActivity, i've a ViewPager with Fragments from which I try to start the next Activity)
Thanks a lot for your help.
My code:
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {
(...)
#Override
protected void onCreate(Bundle savedInstanceState) {
Log.i("TAAG", "MainActivity::onCreate1");
super.onCreate(savedInstanceState);
Log.i("TAAG", "MainActivity::onCreate2");
getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
Log.i("TAAG", "MainActivity::onCreate3");
setContentView(R.layout.activity_main);
Log.i("TAAG", "MainActivity::onCreate4");
(...)
}
Here are the logs:
11-13 18:12:36.442 1098-1098/I/TAAG﹕ MainActivity::onCreate1
11-13 18:12:36.544 1098-1098/I/TAAG﹕ MainActivity::onCreate2
11-13 18:12:36.559 1098-1098/E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: mypackage, PID: 1098
java.lang.RuntimeException: Unable to start activity ComponentInfo{mypackage/mypackage.MainActivity}: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
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.util.AndroidRuntimeException: requestFeature() must be called before adding content
at com.android.internal.policy.impl.PhoneWindow.requestFeature(PhoneWindow.java:301)
at mypackage.MainActivity.onCreate(MainActivity.java:42)
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)
Try calling getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS); before super.onCreate().
I've been playing around with Android Studio and I'm trying to implement a simple chronometer with the Chronometer widget. First I tried this code:
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Chronometer;
import android.view.View;
public class MainActivity extends AppCompatActivity {
Chronometer chrono;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
chrono = (Chronometer) findViewById(R.id.chronometer);
setContentView(R.layout.activity_main);
}
public void startChrono(View view) {
chrono.start();
}
public void stopChrono(View view) {
chrono.stop();
}
}
But when I used it, whenever I pressed the Start button, it would crash the app. Then I found this implementation online:
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Chronometer;
import android.view.View;
public class MainActivity extends AppCompatActivity {
Chronometer chrono;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void startChrono(View view) {
((Chronometer) findViewById(R.id.chronometer)).start();
}
public void stopChrono(View view) {
((Chronometer) findViewById(R.id.chronometer)).start();
}
}
This one works though, can anyone point out the differences between creating the Chronometer object in onCreate as opposed to what the second block of code does?
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4020)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
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.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4015)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
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.Chronometer.start()' on a null object reference
at com.example.mykongee.testchronometer.MainActivity.startChrono(MainActivity.java:22)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4015)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
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)
Your issue is here:
chrono = (Chronometer) findViewById(R.id.chronometer);
setContentView(R.layout.activity_main);
You can not call findViewById before you call setContentLayout, because there is no view to find.
You app would have crashed with a NullPointerException because chrono was null.
In your first example, try swapping these two lines, and it will work the same as the second
setContentView(R.layout.activity_main);
chrono = (Chronometer) findViewById(R.id.chronometer);
In the future, do not simply say it didnt work, Android provides an amazong LogCat that tells you pretty much EXACTLY what the problem is.
If you can not decode the error yourself, then post the stacktrace provided by logcat.
In the first one you are first trying to get a reference to chrono, then you are setting your layout. The thing is, you can't get a reference without setting the layout first (can't find what isn't there...)
false:
chrono = (Chronometer) findViewById(R.id.chronometer);
setContentView(R.layout.activity_main);
correct:
setContentView(R.layout.activity_main);
chrono = (Chronometer) findViewById(R.id.chronometer);
In the second example you are setting the layout, then on button press you find the reference, so everything is ok.