Question

I have two activities. ScreenOne.java and ScreenTwo.java.

ScreenOne extends BaseScreen
ScreenTwo extends ListActivity

I want ScreenTwo to extend BaseScreen as the Back button event makes the app crash.

this.mainListView = getListView();

This is the only line that throws up an error if I change the extension.

The error is:

The method getListView() is undefined for the type ScreenTwo.

My Back button code:

 @Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
     Intent intent = new Intent(getBaseContext(), ScreenThree.class); 
     startActivity(intent); 
        }
        return true;
    }

I need one of the following workarounds:

• Make ScreenTwo extend BaseScreen
• An alternative to the “troublesome” line of code
• Override the Back button to start a new activity.

LogCat Output:

09-07 11:30:13.419: E/AndroidRuntime(2845): FATAL EXCEPTION: main
09-07 11:30:13.419: E/AndroidRuntime(2845): java.lang.ClassCastException: com.example.Droid.Screens.ScreenTwo
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.example.Droid.Services.ScreenService.getCurrentScreen(ScreenService.java:226)
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.example.Droid.Screens.BaseScreen.processKeyDown(BaseScreen.java:310)
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.example.Droid.Main.onKeyDown(Main.java:183)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.view.KeyEvent.dispatch(KeyEvent.java:1256)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.app.Activity.dispatchKeyEvent(Activity.java:2078)
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1709)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2628)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2603)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.view.ViewRoot.handleMessage(ViewRoot.java:1875)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.os.Handler.dispatchMessage(Handler.java:99)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.os.Looper.loop(Looper.java:123)
09-07 11:30:13.419: E/AndroidRuntime(2845): at android.app.ActivityThread.main(ActivityThread.java:3687)
09-07 11:30:13.419: E/AndroidRuntime(2845): at java.lang.reflect.Method.invokeNative(Native Method)
09-07 11:30:13.419: E/AndroidRuntime(2845): at java.lang.reflect.Method.invoke(Method.java:507)
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
09-07 11:30:13.419: E/AndroidRuntime(2845): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
09-07 11:30:13.419: E/AndroidRuntime(2845): at dalvik.system.NativeStart.main(Native Method)

Answer 1

If you are using @android:id/list as an ID of ListView, use:

ListView listView = (ListView) findViewByID(android.R.id.list);

else use:

ListView listView = (ListView) findViewByID(R.id.listView); // the id of your listView given in xml file.

In this way you don’t have to extend the ListActivity.