NullPointerException imageView.setImageBitmap(bitmap)

Question

I'm trying to download an image from a website. This is my code: MainActivity

...
public class MainActivity extends Activity {
public final static String URL = "com.example.test3.URL";
ImageView imageView = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }
}

// execute by pressing button
public void send(View view){
    EditText enter = (EditText) findViewById(R.id.enter);
    String url = enter.getText().toString();
    ImageView imageView = (ImageView) findViewById(R.id.image1);
    new ImageDownload(imageView).execute(url);      
}

}

ImageDownload

public class ImageDownload extends AsyncTask<String, Void, Bitmap>{
ImageView imageView = null;
public ImageDownload(ImageView imageView){
    this.imageView = imageView;
}

/*@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_image_download);

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new    PlaceholderFragment()).commit();
    }
    Intent intent = getIntent();
    String urlString = intent.getStringExtra(MainActivity.URL); */


@Override
protected Bitmap doInBackground(String... url) {
    if(url.length <= 0){        
        return null;
    }
    return downloadBitmap(url[0]);
}

public Bitmap downloadBitmap(String s) {
    String urlString = s;
    URL url;
    InputStream i;
    Bitmap bitmap = null;
    try { 
        url = new URL(urlString);       
        i = url.openStream();
        bitmap = BitmapFactory.decodeStream(i);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e){
        e.printStackTrace();
    }

    return bitmap;
}

public void onPostExecute(Bitmap bitmap){
    Log.d("done", "onPostExecute");
    if(bitmap != null){
        this.imageView.setImageBitmap(bitmap);
    }
}   
}

The program stops with the following log:

05-08 09:52:04.477: D/done(8534): onPostExecute
05-08 09:52:04.477: D/AndroidRuntime(8534): Shutting down VM
05-08 09:52:04.477: W/dalvikvm(8534): threadid=1: thread exiting with uncaught exception (group=0x415e7d88)
05-08 09:52:04.497: E/AndroidRuntime(8534): FATAL EXCEPTION: main
05-08 09:52:04.497: E/AndroidRuntime(8534): Process: com.example.test3, PID: 8534
05-08 09:52:04.497: E/AndroidRuntime(8534): java.lang.NullPointerException
05-08 09:52:04.497: E/AndroidRuntime(8534):     at  com.example.test3.ImageDownload.onPostExecute(ImageDownload.java:90)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at com.example.test3.ImageDownload.onPostExecute(ImageDownload.java:1)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at android.os.AsyncTask.finish(AsyncTask.java:632)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at android.os.Handler.dispatchMessage(Handler.java:102)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at  android.os.Looper.loop(Looper.java:212)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at android.app.ActivityThread.main(ActivityThread.java:5151)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at java.lang.reflect.Method.invokeNative(Native Method)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at java.lang.reflect.Method.invoke(Method.java:515)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
05-08 09:52:04.497: E/AndroidRuntime(8534):     at dalvik.system.NativeStart.main(Native Method)
05-08 09:52:05.707: I/Process(8534): Sending signal. PID: 8534 SIG: 9

fragment_image_download.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="com.example.test3.ImageDownload$PlaceholderFragment" >

<ImageView
  android:contentDescription="@string/desc"
  android:id="@+id/image1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content" >
</ImageView>

</RelativeLayout>

Where does this NullPointerException come from? Can anyone help me please?

Answer 1

The problem here is that you are working with Views inside the fragment incorrectly. send function is a member of Activity class, not the Fragment class, but your ImageView is declared inside the Fragment, so you should provide it's root view (which is not equal to the root view of Activity) before findViewById call. Something like this:

ImageView imageView = getFragmentManager().findFragmentById(...).getView().findViewById(R.id.image1);

But the best solution will be to move all the fragment-related logic inside the Fragment class.

Answer 2

Error comes at line 90 of ImageDownload:

at  com.example.test3.ImageDownload.onPostExecute(ImageDownload.java:90)

Edit:

image1 is present in fragment's layout fragment_main not in activity's layout activity_main, that is the reason for NullPointerException.

Either place your EditText enter in fragment layout or change your image1 access logic.