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Xml button field value is always null

I searched many threads but couldn't understand the problem in my code. I am trying to add setOnClickListener functionality on a button from a fragment. It gives me
nullpointer exception at allNews.setOnClickListener(new View.OnClickListener().
Upon debugging I understand that the variable allNews is null.
Below is my layout code.
<LinearLayout
android:layout_gravity="center"
android:gravity="center"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id = "#+id/b_all"
android:layout_width="70dp"
android:layout_height="70dp"
android:gravity="center"
android:text="All \n news"
android:textColor="#FFF"
android:textSize="15sp"
android:background="#drawable/button_bg_round"
android:padding="5dp"
android:textAllCaps="false"
/>
And here is my java code:
public class CategoriesFragment extends Fragment {
public Button allNews;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
public View onCreateView(final LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_news_menu, container, false);
getActivity().setTitle("Play");
allNews = (Button) rootView.findViewById(R.id.b_all);
return rootView;
}
public void onViewCreated(View view, #android.support.annotation.Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
allNews.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
startActivity(new Intent(getActivity(), Newsmain.class));
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
I am unable to understand what am I missing. There is a scrollview inside the same xml. Should we handle such layouts/fields seperately ?
Any help in this regard is highly appreciated.
Thanks
Satya
SOLVED: I renamed the xml with activity_news_category and then the variable is not null anymore. Prev the xml was named as activity_news_menu. Thnx for all who attempted to help.

public View onCreateView(final LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_news_menu, container, false);
getActivity().setTitle("Play");
allNews = (Button) rootView.findViewById(R.id.b_all);
allNews.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
startActivity(new Intent(getActivity(), Newsmain.class));
} catch (Exception e) {
e.printStackTrace();
}
}
});
return rootView;
}
Use set onclicklistener in OncreateView method.Hope this helps

public void onViewCreated(View view, #android.support.annotation.Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
allNews = (Button) view.findViewById(R.id.b_all);
allNews.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
startActivity(new Intent(getActivity(), Newsmain.class));
} catch (Exception e) {
e.printStackTrace();
}
}
});
UPDATE:
instead of rootView it should be view
Add allNews = (Button) rootView.findViewById(R.id.b_all); in onViewCreated() and remove it from onCreateView()

1) Close the LinearLayout properly.
2) Remove the space between the android:id = "#+id/b_all", so you have:
<LinearLayout
android:layout_gravity="center"
android:gravity="center"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/b_all"
android:layout_width="70dp"
android:layout_height="70dp"
android:gravity="center"
android:text="All \n news"
android:textColor="#FFF"
android:textSize="15sp"
android:background="#drawable/button_bg_round"
android:padding="5dp"
android:textAllCaps="false"
/>
</LinearLayout>
Then rebuild the project.

Start a game loop with button push

I have created an activity PlayActivity that starts a new thread and a game loop. When I have this class as my launcher activity (MainActivity) it works perfectly. But I obviously do not want my app to start with the game loop! In my MainActivity I have different tabs as fragments, in my Home tab, I have a button. I want the game to start with the button clicked. Here is my PlayActivity:
public class PLayActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN );
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
Constants.SCREEN_WIDTH = dm.widthPixels;
Constants.SCREEN_HEIGHT = dm.heightPixels;
try {
InputStream is = getAssets().open("test 3.xml");
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
setContentView(new PlayPanel(this, is));
} catch(IOException e) {e.printStackTrace();}
}
}
Main Activity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View inflatedView = getLayoutInflater().inflate(R.layout.home, null);
basic = (Button) inflatedView.findViewById(R.id.basic);
intermediate = (Button) inflatedView.findViewById((R.id.intermidiate));
basic.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg) {
// Start NewActivity.class
Intent basicIntent = new Intent(MainActivity.this, PLayActivity.class);
startActivity(basicIntent);
}
});
Home.java:
public class Home extends Fragment {
Button basic;
Button intermediate;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.home, container, false);
return view;
}
}
and home.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">
<Button
android:text="Basic"
android:layout_width="match_parent"
android:layout_height="180dp"
android:layout_marginTop="0dp"
android:id="#+id/basic"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<Button
android:text="Intermidiate"
android:layout_width="match_parent"
android:layout_height="180dp"
android:layout_marginTop="0dp"
android:id="#+id/intermidiate"
android:layout_below="#+id/basic"
android:layout_centerHorizontal="true" />
<Button
android:text="Advanced"
android:layout_width="match_parent"
android:layout_height="180dp"
android:layout_marginTop="0dp"
android:id="#+id/advanced"
android:layout_below="#+id/intermidiate"
android:layout_centerHorizontal="true" />
</RelativeLayout>
When I click the button nothing happens! What should I do?

cannot open a webpage through imagebutton - android studio

the following is my java file for one of the fragments that am using to have multiple image buttons which open multiple weebpages.
please help.
treat me as a noob.
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.menu8_layout, container, false);
return rootview;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Button bt1 = (Button) findViewById(R.id.btn_click_login);
btn_login.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
}
Intent myWebLink = new Intent(android.content.Intent.ACTION_VIEW);
myWebLink.setData(Uri.parse("http://google.com"));
startActivity(myWebLink);
});
}
}
here is the related xml file.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/bt1"
android:clickable="true"
android:autoLink="web"
android:cursorVisible="true"
android:linksClickable="true"
android:onClick="goToSo"
android:text="some" />

DialogFragment: button.setOnClickListener throws NullPointerException

I have an Activity with a button like this:
<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"
tools:context=".MainActivity">
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:onClick="onButtonClickListener"
android:text="Show Fragment" />
</RelativeLayout>
And my onButtonClickListener method from xml is(here I create the DialogFragment and set onClickListener for a clear button from dialog):
public void onButtonClickListener(View view) {
FragmentManager fm = getFragmentManager();
MyDialogFragment dialogFragment = new MyDialogFragment ();
dialogFragment.show(fm, "Sample Fragment");
final EditText messageText = (EditText) findViewById(R.id.editText);
Button clearButton = (Button) findViewById(R.id.button_clear);
clearButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
messageText.setText(null);
}
});
}
My problem is that when DialogFragment shows it throws NullPointerException:
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.cristi.dialogfragmenttest2.MainActivity.onButtonClickListener(MainActivity.java:51)
At this line of code: clearButton.setOnClickListener(new View.OnClickListener() {
My xml for DialogFragment is:
<?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">
<EditText
android:id="#+id/editText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:maxLength="200" />
<Button
android:id="#+id/button_clear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Clear"
android:layout_below="#+id/editText"
android:layout_centerHorizontal="true" />
</RelativeLayout>
What could be the problem with the setOnClickListener? Why does it says that my button from DialogFragment is null?
Any reference or advice is welcome! Thanks in advance!
Edit:
-MyDialogFragment code:
public class MyDialogFragment extends DialogFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.dialog_fragment, container, false);
getDialog().setTitle("Enter message");
return rootView;
}

You must have refernece to the root view where is your button button_clear, then call rootView.findViewById(...) to get the button reference...
Solution:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.dialog_fragment, container, false);
getDialog().setTitle("Enter message");
Button clearButton = (Button) rootView.findViewById(R.id.button_clear);
clearButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
messageText.setText(null);
}
});
return rootView;
}

visibility gone of image view when come from 2nd activity to 1st activity using putextra and getextra method in android

everyone. I am new in android. I am creating two activities in android ,1st activity has two image view and one button . and 2nd activity has one button. when I go to second activity and then from second activity agian . one image view of 1st activity should visibility gone. how can i do this.
here is my code
Activitymain.xml
<ImageView
android:id="#+id/1stimage"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ImageView
android:id="#+id/2ndimage"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="go to second activity" />
mainactivity.java
ImageView imageView1, imageView2;
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView1 = (ImageView) findViewById(R.id.1stimage);
imageView2 = (ImageView) findViewById(R.id.2ndimage);
btn = (Button) findViewById(R.id.btn1);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent Firstintent= new Intent(MainActivity.this,SecondActivity.class);
startActivity(Firstintent);
}
});
}
secondactivity.xml
<Button
android:id="#+id/btn2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="go to 1st activity" />
secondactivity.java
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
btn = (Button) findViewById(R.id.btn2);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent SecondIntent = new Intent(SecondActivity.this,
MainActivity.class);
SecondActivity.this.startActivity(SecondIntent);
SecondActivity.this.finishActivity();
}
});
}
please help me

Activitymain.xml
<ImageView
android:id="#+id/1stimage"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ImageView
android:id="#+id/2ndimage"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="go to second activity" />
mainactivity.java
ImageView imageView1, imageView2;
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView1 = (ImageView) findViewById(R.id.1stimage);
imageView2 = (ImageView) findViewById(R.id.2ndimage);
btn = (Button) findViewById(R.id.btn1);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent Firstintent= new Intent(MainActivity.this,SecondActivity.class);
startActivity(Firstintent);
}
});
Bundle extras = getIntent().getExtras();
if(extras != null){
if(extras.getBoolean("isResult", false)){
imageView1.setVisability(View.GONE);
}
}
}
secondactivity.xml
<Button
android:id="#+id/btn2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="go to 1st activity" />
secondactivity.java
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
btn = (Button) findViewById(R.id.btn2);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent SecondIntent = new Intent(SecondActivity.this,
MainActivity.class);
SecondIntent.putExtra("isResult", true);
SecondActivity.this.startActivity(SecondIntent);
SecondActivity.this.finishActivity();
}
});
}

Use putextra(tag, some variable to use in mainActivity) and Bundle extras = getIntent().getExtras(); extras.get[type of variable](tag) to pass a variable (probably a boolean) to tell the onCreate() to show or not show the pic.
EDIT:
Here is one way to implement it: in the first activity:
1) Check if there are extras (A.K.A. if second activity was loaded/ there is a true)
2) If (yes) { if (first pic is loaded) { remove first pic } else if (first pick is not but second is loaded) { remove second pic } ... for all the pictures you want to do this to.
Remember you only need to pass true/false from the second activity (and then handle it in the first/one being modified)