Develop Reference

Button onClick() only matches in mainActivity [duplicate]

This question already has answers here:
Android app crashing (fragment and xml onclick)
(5 answers)
How to handle button clicks using the XML onClick within Fragments
(19 answers)
Android Fragment onClick button Method
(7 answers)
Closed 4 years ago.
I have a button in activity_welcome.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".WelcomeActivity">
<Button
android:id="#+id/signIn"
android:layout_width="270dp"
android:layout_height="39dp"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="5"
android:text="註冊"
android:textColor="#000000"
android:textSize="20sp"
android:onClick="goToSignUpOne"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.602" />
</android.support.constraint.ConstraintLayout>
When I call my goToSignUpOne method in the WelcomeActivity class, it causes a crash and it seems like which doesn't match the method. This is the code of the goToSignUpOne function:
public void goToSignUpOne(View view) {
setContentView(R.layout.activity_sign_up_one);
}
After using goToSignUpOne to navigate to my MainActivity, it works!
So my button is in the activity_welcome.xml but corresponds to MainActivity? Is that right? I think it should rather correspond to the activity which the XML is for.
error log
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.faketsao.dating, PID: 21004
java.lang.IllegalStateException: Could not find method goToSignUpOne(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'signIn'
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:423)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:380)
at android.view.View.performClick(View.java:6205)
at android.widget.TextView.performClick(TextView.java:11103)
at android.view.View$PerformClick.run(View.java:23653)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6682)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1534)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1424)
WelcomeActivity
package com.example.faketsao.dating;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
public class WelcomeActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_welcome);
}
public void goToSignUpOne(View view) {
setContentView(R.layout.activity_sign_up_one);
}
}

What you are doing is a pretty non-typical approach. If I were you, I would define the onClick in the code of WelcomeActivity, and not in the XML, since using the XML is prone to produce errors like yours. Therefore, the code of your WelcomeActivity should be something like this:
public class WelcomeActivity extends AppCompatActivity {
private View.OnClickListener onButtonClick = new View.OnClickListener(){
#Override
public void onClick(View v){
goToSignUpOne(v);
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_welcome);
Button button = (Button) findViewById(R.id.signUp);
button.setOnClickListener(onButtonClick);
}
public void goToSignUpOne(View view) {
setContentView(R.layout.activity_sign_up_one);
}
}
In the XML, you remove the line android:onClick="goToSignUpOne" under your Button, and then that should work.
In case you didn't only want to change the view, but start a new activity instead, just make the goToSignUpOne(View) function like this:
public void goToSignUpOne(View view) {
startActivity(new Intent(this, SignUpOneActivity.class));
}
Hope this is what you were looking for! :D

Implementing a WebView within a CardView using a RecyclerView [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I am using a WebView within a CardView with Recyclerview.
I implemented them correctly, but the problem is that when I run application it crashes and shows a nullpointer exception,
Log crash report:
java.lang.RuntimeException: Unable to start activity ComponentInfo{andro.petrochemical/andro.petrochemical.webViewNews}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.webkit.WebView.setWebViewClient(android.webkit.WebViewClient)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.webkit.WebView.setWebViewClient(android.webkit.WebViewClient)' on a null object reference
at andro.petrochemical.webViewNews.onCreate(webViewNews.java:33)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
WebView CardView xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<WebView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/webView_news"/>
</LinearLayout>
</android.support.v7.widget.CardView>
RecyclerView xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="android.support.v7.widget.LinearLayoutManager"
android:id="#+id/resycleWeb"/>
</LinearLayout>
WebView java class file:
public class webViewNews extends AppCompatActivity {
private WebView webviewthis;
private RecyclerView webVieRes;
private DatabaseReference mdataRef;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.webview_page);
webVieRes = (RecyclerView) findViewById(R.id.resycleWeb);
mdataRef = FirebaseDatabase.getInstance().getReference().child("weber");
webviewthis = (WebView)findViewById(R.id.webView_news);
webviewthis.setWebViewClient(new WebViewClient());
webviewthis.getSettings().setJavaScriptEnabled(true);
webviewthis.getSettings().setLoadsImagesAutomatically(true);
}
#Override
public void onStart() {
super.onStart();
FirebaseRecyclerAdapter<post2web,post2webViewHolder> firebaseRecyclerAdapte = new FirebaseRecyclerAdapter<post2web,post2webViewHolder>(
post2web.class,
R.layout.web_card,
post2webViewHolder.class,
mdataRef
) {
#Override
protected void populateViewHolder(post2webViewHolder viewHolder, post2web model, int position) {
viewHolder.setWebViewPost(model.getWebViewPost());
}
};
webVieRes.setAdapter(firebaseRecyclerAdapte);
}
public static class post2webViewHolder extends RecyclerView.ViewHolder {
View mVie;
public post2webViewHolder(View itemView) {
super(itemView);
mVie = itemView;
}
public void setWebViewPost(String webViewPost) {
WebView post_web = (WebView) mVie.findViewById(R.id.webView_news);
post_web.loadUrl(webViewPost);
}
}
}

Remove webview initialization from onCreate()
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.webview_page);
webVieRes = (RecyclerView) findViewById(R.id.resycleWeb);
mdataRef = FirebaseDatabase.getInstance().getReference().child("weber");
}
And update in post2webViewHolder
public void setWebViewPost(String webViewPost) {
WebView post_web = (WebView) mVie.findViewById(R.id.webView_news);
post_web.loadUrl(webViewPost);
post_web.setWebViewClient(new WebViewClient());
post_web.getSettings().setJavaScriptEnabled(true);
post_web.getSettings().setLoadsImagesAutomatically(true);
}

You need to only find the WebView from the post2webViewHolder
It's not part of the Activity, therefore it's null
Remove webviewthis

I create class about toolbar and I can't use it in several activity

public class ToolBarNavigation extends AppCompatActivity {
public void exe (int address){
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.MATCH_PARENT,
RelativeLayout.LayoutParams.WRAP_CONTENT);
RelativeLayout relativeLayout = (RelativeLayout) findViewById(address);
LayoutInflater layoutInflater = (LayoutInflater) getBaseContext().getSystemService(getBaseContext().LAYOUT_INFLATER_SERVICE);
View view = layoutInflater.inflate(R.layout.toolbar_navigation, null);
lp.addRule(RelativeLayout.ALIGN_PARENT_TOP);
view.setLayoutParams(lp);
relativeLayout.addView(view);
}
}
public class MainActivity extends AppCompatActivity {
ToolBarNavigation t1 = new ToolBarNavigation();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
t1.exe(R.id.relativeLayout1);
}
}
Error:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.m01nyabesh.yabesh/com.m01nyabesh.yabesh.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.app.Activity.findViewById(Activity.java:1853)
at com.m01nyabesh.yabesh.ToolBarNavigation.exe(ToolBarNavigation.java:16)
at com.m01nyabesh.yabesh.MainActivity.onCreate(MainActivity.java:24)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
at android.app.ActivityThread.access$600(ActivityThread.java:141) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:137) 
at android.app.ActivityThread.main(ActivityThread.java:5103) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke

If you want to use default toolbar in Different activity do following (Source code taken from previous project and I using Butterknife && Android SupportDesign):
First create BaseActivity.java Class like:
public abstract class BaseActivity extends AppCompatActivity {
#BindView(R.id.toolbar)
Toolbar toolbar;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//rest of common initialization may goes here
}
protected void setupToolbar() {
setSupportActionBar(toolbar);
ActionBar ab = getSupportActionBar();
if (ab != null) {
ab.setDisplayHomeAsUpEnabled(true);
ab.setDisplayShowHomeEnabled(true);
}
}
}
Then define your own activity and extend from BaseActivity.java something like:
public class MyActivity extends BaseActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity);
ButterKnife.bind(this);
setupToolbar();
}
#Override
protected void setupToolbar() {
super.setupToolbar();
setTitle(R.string.title_activity);
}
}
In your activity.xml include your default Toolbar like:
<?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"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/default_bg"
android:fitsSystemWindows="true">
<include layout="#layout/include_toolbar_default" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<!-- other ui element goes here -->
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>
And this is your include_toolbar_default.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.AppBarLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:elevation="0dp">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:contentInsetStartWithNavigation="0dp"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
</android.support.design.widget.AppBarLayout>

maybe you are creating the toolbar before the activity is created,
try to create the toolbar inside OnCreate function, and you dont show if the layout activity_main, cointains a toolbar, you should get the reference of the layout and then inflate that view with your custom code

No actionBar with app-compat-v21 library in preferenceactivity?

I'm having problem with ActionBar and app-compat-v21.
ActionBar is shown everywhere except PreferenceActivity
I tried to follow recommendations and made it with Fragments:
public class PrefsFragment extends PreferenceFragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
}
}
and
public class PrefsActivity extends PreferenceActivity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getFragmentManager().beginTransaction()
.replace(android.R.id.content, new PrefsFragment()).commit();
}
}
However, there's no ActionBar.
BTW, in Styles.xml is set <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
What's wrong?

In order to use the new appcompat v21 you have to:
extend the AppCompatActivity
use a theme which inherits from Theme.AppCompat.(for example Light or NoActionBar)
The PreferenceActivity doesn't extend the AppCompatActivity.
It is the reason why there is no actionbar in your code.
As solution you can create a PreferenceFragment as you are doing and use it in a standard AppCompatActivity.
UPDATED 12/06/2015
With the new 22.1+ appcompat you can use also the AppCompatDelegate to extend AppCompat's support to any Activity.
You can check this official link to AppCompatPreferenceActivity, where you can find an example of this technique.

With the app compat the toolbar needs to be defined in the layout. You can create a layout for the Settings Activity with the toolbar and then add the preference fragment.
For example:
activity_settings.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<include xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/toolbar"
layout="#layout/toolbar" />
<fragment
android:id="#+id/settings_fragment"
android:name="com.bla.bla.MyPreferenceFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/toolbar" />
</RelativeLayout>
SettingsActivity:
public class SettingsActivity extends ActionBarActivity{
#Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
Toolbar actionbar = (Toolbar) findViewById(R.id.toolbar);
actionbar.setTitle("Settings");
actionbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
SettingsActivity.this.finish();
}
});
}
MyPreferenceFragment:
public static class MyPreferenceFragment extends PreferenceFragment {
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);;
}
}
edit: Updated the answer to use ActionBarActivity instead of the deprecated PreferenceActivity

Using customview from library in project

I have CustomLayout class declared in a library customAndroidLibrary. This CustomLayout extends ViewGroup. Now I want to use this CustomLayout in my layout.xml which is in my project. I have included this library in my project.
CustomLayout class
package com.android.custom;
public class CustomLayout extends ViewGroup {
.....
}
layout.xml
<com.android.custom.CustomLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/animation_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</com.android.custom.CustomLayout>
MainActivity
package com.android.ui;
public class MainActivity extends Activity{
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.layout);
}
}
But it is throwing ClassNotFoundException.
Even it is not detecting my Activity also if I am using the custom view in layout.xml
If I am using simple TextView in layout.xml. Then it is not giving any error.

Solved it on my own.
<com.android.custom.CustomLayout
xmlns:android="http://schemas.android.com/apk/res/android"
class="com.android.custom.CustomLayout"
android:id="#+id/animation_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</com.android.custom.CustomLayout>