Android: Multitouch on 2 Images in a View

Question

Currently, I have a Problem while using a MultitouchView. I mainly use the Multitouchview how it is made here: http://www.vogella.com/articles/AndroidTouch/article.html My Problem is, that i have 2 Imageviews in my Layout and I want to only take action if both are touched. I tried finding them by getting the positions (top, left, bottom, right), but it always returns a nullpointer-exception. However, I already tried getting them in the multitouchView like this:

ImageView leftImage =(ImageView) findViewById(R.id.leftAlert);
int topLeft = leftImage.getTop();
int botLeft = leftImage.getBottom();
int leftLeft = leftImage.getLeft();
int rightLeft = leftImage.getRight();
ImageView rightImage =(ImageView) findViewById(R.id.rightAlert);
int topRight = rightImage.getTop();
int botRight = rightImage.getBottom();
int leftRight = rightImage.getLeft();
int rightRight = rightImage.getRight();

Since that didn't work I also already tried getting the positions in my Main Activity the same way and returning them with getters like this:

    MainActivity Views = new MainActivity();

int topLeft= Views.getTopLeft(); 
int botLeft=Views.getBotLeft();
int leftLeft=Views.getleftLeft();
int rightLeft=Views.getRightLeft();
int topRight=Views.getTopRight();
int botRight=Views.getBotRight();
int leftRight=Views.getleftRight();
int rightRight=Views.getRightRight();

And in the Main Activity:

ImageView leftImage =(ImageView) findViewById(R.id.leftAlert);
int topLeft = leftImage.getTop();
int botLeft = leftImage.getBottom();
int leftLeft = leftImage.getLeft();
int rightLeft = leftImage.getRight();
ImageView rightImage =(ImageView) findViewById(R.id.rightAlert);
int topRight = rightImage.getTop();
int botRight = rightImage.getBottom();
int leftRight = rightImage.getLeft();
int rightRight = rightImage.getRight();

public int getTopLeft(){
    return topLeft;
}

public int getBotLeft(){
    return botLeft;
}

public int getleftLeft(){
    return leftLeft;
}

public int getRightLeft(){
    return rightLeft;
}

public int getTopRight(){
    return topLeft;
}

public int getBotRight(){
    return botLeft;
}

public int getleftRight(){
    return leftLeft;
}

public int getRightRight(){
    return rightLeft;
}

I am still learning Android (this is a project for my college) so if someone has an easy solution I would be very glad.

Also I am using a very Old phone for Testing, so i can't really use the functions getX or getY for my Image (currently using API Level 9).

Currently I'm fiddling with onTouchListeners on my Images, but I feel like it should work like this, so I want to know why it doesn't for me.

If needed here's my MultiTouchView.class as it is:

     package com.example.webanwendungengps;
     import android.content.Context;
     import android.graphics.PointF;
     import android.util.AttributeSet;
     import android.util.SparseArray;
     import android.view.MotionEvent;
     import android.view.View;
     import android.widget.Toast;
     //this entire class is a View, that is able to handle multiple touches on a Screen
     public class MultitouchView extends View {

     MainActivity Views = new MainActivity();

    int topLeft= Views.getTopLeft(); 
    int botLeft=Views.getBotLeft();
    int leftLeft=Views.getleftLeft();
    int rightLeft=Views.getRightLeft();
    int topRight=Views.getTopRight();
    int botRight=Views.getBotRight();
    int leftRight=Views.getleftRight();
    int rightRight=Views.getRightRight();

     private SparseArray<PointF> mActivePointers;

     public MultitouchView(Context context, AttributeSet attrs) {
     super(context, attrs);
     initView();   
     } 

     private void initView() {
      mActivePointers = new SparseArray<PointF>();
     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {

     // get pointer index from the event object
     int pointerIndex = event.getActionIndex();

     // get pointer ID
     int pointerId = event.getPointerId(pointerIndex);

     // get masked (not specific to a pointer) action
     int maskedAction = event.getActionMasked();

     switch (maskedAction) {

     case MotionEvent.ACTION_DOWN:{
      float posX=event.getX();
      float posY=event.getY();


      if ((posX > leftLeft && posX <rightLeft && posY>botLeft && posY>topLeft)|| 
              (posX > leftRight && posX <rightRight && posY>botRight && posY>topRight)){
          ShowToast();  
      }
    }
    case MotionEvent.ACTION_POINTER_DOWN: {
      if(event.getPointerCount()>=2){
          float posX2=event.getX();
          float posY2=event.getY();
          if ((posX2 > leftLeft && posX2 <rightLeft && posY2>botLeft && posY2>topLeft)|| 
                  (posX2 > leftRight && posX2 <rightRight && posY2>botRight && posY2>topRight) ){
              ShowToast();  
          }
      }      
      break;
     }

    case MotionEvent.ACTION_MOVE: { // a pointer was moved
    }
    case MotionEvent.ACTION_UP: {
   //Do Nothing
    }
    case MotionEvent.ACTION_POINTER_UP: {
        //Do Nothing

    }
    case MotionEvent.ACTION_CANCEL: {
      mActivePointers.remove(pointerId);

      break;
    }
    }

    invalidate();
    return true;
  }

private void ShowToast() {
            Toast.makeText(getContext(), "Test", Toast.LENGTH_SHORT).show();
}

} 

Answer 1

Please had a look on the below links. It may give you an idea for your project.

Android Multitouch

multitouch demo

multitouch handling

Multitouch in android