Question

I have the following function that is called after a menu item is clicked. Basically I have some string which I try to set to a TextView located inside an AlertDialog.

public void createAboutDialog() {
    View layout = mContext.getSystemService(LAYOUT_INFLATER_SERVICE).inflate(R.layout.about, null);

    TextView tv = (TextView) findViewById(R.id.myTextView);
    tv.setText("My text here");

    AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
    builder.setView(layout);

    AlertDialog alertDialog = builder.create();
    alertDialog.show();
}

The issue appears to be related to the setText() call.

LogCat

08-01 14:19:33.423: D/MainActivity(1793): 1.0
08-01 14:19:33.473: D/AndroidRuntime(1793): Shutting down VM
08-01 14:19:33.473: W/dalvikvm(1793): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
08-01 14:19:33.603: E/AndroidRuntime(1793): FATAL EXCEPTION: main
08-01 14:19:33.603: E/AndroidRuntime(1793): java.lang.NullPointerException
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.example.your.chinese.name.MainActivity.createAboutDialog(MainActivity.java:105)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.example.your.chinese.name.MainActivity.onOptionsItemSelected(MainActivity.java:74)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.app.Activity.onMenuItemSelected(Activity.java:2502)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:969)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.view.menu.ListMenuPresenter.onItemClick(ListMenuPresenter.java:163)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.widget.AdapterView.performItemClick(AdapterView.java:292)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.widget.AbsListView.performItemClick(AbsListView.java:1065)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2522)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.widget.AbsListView.onTouchEvent(AbsListView.java:3195)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.View.dispatchTouchEvent(View.java:5564)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2052)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1813)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2058)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1827)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1879)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.View.dispatchPointerEvent(View.java:5766)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:2890)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2466)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewRootImpl.processInputEvents(ViewRootImpl.java:845)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2475)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.os.Looper.loop(Looper.java:137)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at android.app.ActivityThread.main(ActivityThread.java:4441)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at java.lang.reflect.Method.invokeNative(Native Method)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at java.lang.reflect.Method.invoke(Method.java:511)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-01 14:19:33.603: E/AndroidRuntime(1793):     at dalvik.system.NativeStart.main(Native Method)
08-01 14:19:35.583: I/Process(1793): Sending signal. PID: 1793 SIG: 9

Answer 1

You need to call findViewById() from the correct context:

TextView tvVersion = (TextView) layout.findViewById(R.id.tvAboutdialogVersion);

If not provided, it will be called from the Activity context, which has loaded the main XML view and it doesn’t have access/reference to the dialog’s XML (and its TextViews) which you just inflated.