Question

My Main Activity extends ListActivity and displays a List. I am using custom Listitems defined in a class named DefinitionAdapter.
I also have a seperate class that implements OnClickListener.

In the class DefinitionAdapter I set the OnClickListener to the ListItems:

   public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null) {
            LayoutInflater vi = (LayoutInflater)getContext().getSystemService(
                    Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.row, null);
        }
...

        v.setOnClickListener(new OnItemClickListener(position) );

        return v;
   }

My custom OnClickListener is supposed to start another activity.

public class OnItemClickListener implements OnClickListener extends Activity {


    private int position;

    public OnItemClickListener(int p) {

        position = p;   
    }

    @Override
    public void onClick(View v) {

        Intent intent = new Intent(this, ShowDefinition.class);
        startActivity(intent);

    }

}

I am not sure that I am doing that right. I added my new activity to the manifest, as well as the activity i extended the listener with:

<activity android:name="ShowDefinition" android:label="@string/app_name">
</activity>
<activity android:name="OnItemClickListener" android:label="@string/app_name">
</activity>    

Nonetheless, if I click on an Item in my List, the application always breaks with a NullPointerException. I think I am using the intent wrong… any Ideas?

In regard to Nikita Beloglazov’s comment:

It breaks when I create the Intent:

Intent intent = new Intent(this, ShowDefinition.class);

Here’s the stacktrace:

05-23 22:56:46.629: ERROR/AndroidRuntime(258): Uncaught handler: thread main exiting due to uncaught exception
05-23 22:56:46.659: ERROR/AndroidRuntime(258): java.lang.NullPointerException
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.content.ComponentName.<init>(ComponentName.java:75)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.content.Intent.<init>(Intent.java:2551)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.andiandy.juradefinitions.OnItemClickListener.onClick(OnItemClickListener.java:22)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.View.performClick(View.java:2364)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.View.onTouchEvent(View.java:4179)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.View.dispatchTouchEvent(View.java:3709)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:852)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.os.Looper.loop(Looper.java:123)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at android.app.ActivityThread.main(ActivityThread.java:4363)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at java.lang.reflect.Method.invokeNative(Native Method)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at java.lang.reflect.Method.invoke(Method.java:521)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-23 22:56:46.659: ERROR/AndroidRuntime(258):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

Your OnItemClickListener should not extend Activity. Instead, you should arrange for the OnItemClickListener to have access to your ListActivity instance. Any view that is already part of the activity (like the ListView) has access to the ListActivity instance via getContext(). Then implement onClick like this:

@Override
public void onClick(View v) {
    Intent intent = new Intent(context, ShowDefinition.class);
    context.startActivity(intent);
}