public class MyCustomView extends ImageView implements OnTouchListener {
    Bitmap bitmap;
    Canvas bitmapCanvas;
    Paint paint = new Paint();

    public MyCustomView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }
    public MyCustomView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    public MyCustomView(Context context) {
        super(context);
        init();
    }
    public void init() {
        this.setOnTouchListener(this);
        setFocusable(true);
        setFocusableInTouchMode(true);
        
        paint.setColor(Color.WHITE);
        paint.setAntiAlias(true);
        paint.setStyle(Style.FILL_AND_STROKE);
        
        int width = 200; 
        int height = 200; 
        bitmap = Bitmap.createBitmap (width,height,Config.RGB_565);
        
        bitmapCanvas = new Canvas();
        bitmapCanvas.setBitmap(bitmap);
        bitmapCanvas.drawColor(Color.CYAN);
        
        bitmapCanvas.drawText("Test", 10, 10, paint);
        
        bitmapCanvas.drawLine(0, 100, 200, 100, paint);
        bitmapCanvas.drawLine(100, 0, 100, 200, paint);
        this.setImageBitmap(bitmap);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
    }
    
    public boolean onTouch(View view, MotionEvent event)
    {
        bitmapCanvas.drawCircle(event.getX(), event.getY(), 5, paint);
        invalidate();
        return true;
    }
}

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/linearLayout1" android:layout_height="fill_parent" android:orientation="vertical" android:layout_width="fill_parent">
        <de.Koordinaten.MyCustomView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/imageView1" android:layout_width="wrap_content" android:layout_height="wrap_content"/>
        <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/textView1" android:text="TextView"></TextView>
        <Button android:text="Reset" android:id="@+id/btnReset" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
    </LinearLayout>