Question

I am new to Andriod and having difficult time adding controls (Views) on top of my GLSurfaceView.I want this to be added on a corner. (say bottom-right)
Initially I wanted to add Joystick like widget,but at first I wanted to add “Left”,”Right”,”Top”,”Down” buttons.
I created a layout XML file as below :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <View
        android:id="@+id/viewControls"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/relativeLayout1"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true" />

    <RelativeLayout
        android:id="@+id/relativeLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_centerVertical="true"
        android:layout_marginLeft="140dp" >
    </RelativeLayout>

    <Button
        android:id="@+id/buttonR"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/relativeLayout1"
        android:text="R" />

    <Button
        android:id="@+id/buttonL"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="L" />

</RelativeLayout>

And in my Activity ,I tried as follows:

public class MyOpenGL2Activity extends Activity {

    private GLSurfaceView mGLview;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

        mGLview=new MyOpenGL2SurfaceView(this);

        FrameLayout flayout=new FrameLayout(this);     
        flayout.addView(mGLview);

        View controller=findViewById(R.id.viewControls);

        flayout.addView(controller);       


        setContentView(flayout);
}
...

But the application crashes saying

05-05 14:40:08.015: W/dalvikvm(2258): threadid=1: thread exiting with
uncaught exception (group=0x40a841f8) 05-05 14:40:08.023:
E/AndroidRuntime(2258): FATAL EXCEPTION: main 05-05 14:40:08.023:
E/AndroidRuntime(2258): java.lang.RuntimeException: Unable to start
activity ComponentInfo{ausoft.opengl/ausoft.opengl.MyOpenGL2Activity}:
java.lang.NullPointerException 05-05 14:40:08.023:
E/AndroidRuntime(2258): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.app.ActivityThread.access$600(ActivityThread.java:122) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.os.Handler.dispatchMessage(Handler.java:99) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
android.os.Looper.loop(Looper.java:137) 05-05 14:40:08.023:
E/AndroidRuntime(2258): at
android.app.ActivityThread.main(ActivityThread.java:4340) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
java.lang.reflect.Method.invokeNative(Native Method) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
java.lang.reflect.Method.invoke(Method.java:511) 05-05 14:40:08.023:
E/AndroidRuntime(2258): at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
dalvik.system.NativeStart.main(Native Method) 05-05 14:40:08.023:
E/AndroidRuntime(2258): Caused by: java.lang.NullPointerException
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.view.ViewGroup.addView(ViewGroup.java:3165) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
android.view.ViewGroup.addView(ViewGroup.java:3152) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
ausoft.opengl.MyOpenGL2Activity.onCreate(MyOpenGL2Activity.java:35)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.app.Activity.performCreate(Activity.java:4465) 05-05
14:40:08.023: E/AndroidRuntime(2258): at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
05-05 14:40:08.023: E/AndroidRuntime(2258): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
05-05 14:40:08.023: E/AndroidRuntime(2258): … 11 more

Any tips?

Answer 1

You are trying to findViewById(R.id.viewControls); but you have not called setContentView() before… Where is the view viewControls ?

---

If you want, you can create the view like this

View controller = new View(this.getApplicationContext());

or whatever…