将人像旋转到风景时，我要关闭力量，我尝试了android：configChanges =“ keyboard | keyboardHidden”并以人像模式工作吗？

Question

AM getting force close on emulator while rotating from portrait to Landscape? I already tried adding in manifest android:configChanges="keyboard|keyboardHidden"

02-05 17:29:52.321: E/AndroidRuntime(1192): FATAL EXCEPTION: main
02-05 17:29:52.321: E/AndroidRuntime(1192): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kidzapp.sample/com.kidzapp.sample.alphabets}: java.lang.NullPointerException
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.os.Looper.loop(Looper.java:123)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread.main(ActivityThread.java:4627)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at java.lang.reflect.Method.invokeNative(Native Method)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at java.lang.reflect.Method.invoke(Method.java:521)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at dalvik.system.NativeStart.main(Native Method)
02-05 17:29:52.321: E/AndroidRuntime(1192): Caused by: java.lang.NullPointerException
02-05 17:29:52.321: E/AndroidRuntime(1192):     at com.kidzapp.sample.alphabets.onCreate(alphabets.java:68)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-05 17:29:52.321: E/AndroidRuntime(1192):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)

This is my code:

public class alphabets extends Activity implements OnClickListener{

    ImageButton home;
    @Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.lower);

          home=(ImageButton)findViewById(R.id.home);

        home.setOnClickListener(this);
}

 public void onClick(View image) {
        // TODO Auto-generated method stub

switch (image.getId()) {
case R.id.home:

Intent i=new Intent(this, MainActivity.class);

startActivity(i);
finish();
break;

    }

}

@Override
protected void onStop() {
    // TODO Auto-generated method stub
    mp.stop();
    super.onStop();
}

Answer 1

It seems that your ImageView home view is NULL that why when you try to set your clickListener it crashes:

home.setOnClickListener(this);

If it only occurs when you are in landscape mode, I think it's because you are using a specific layout for landscape orientation (directory res/layout-land ) and this layout does not have an ImageView with the R.id.home identifier.

Edit:

One more thing, you do not need to add android:configChanges="keyboard|keyboardHidden" to your manifest. It's not the cause of your problem and it's discouraged for Android development expect for some really specific case.

In the official documentation :

This technique should be considered a last resort when you must avoid restarts due to a configuration change and is not recommended for most applications.