Pinching Zoom in android Image View or Bitmap

Pinching Zoom in android Image View or Bitmap

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main class TouchImageView.java

 package com.ahmad;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Matrix;
 import android.graphics.PointF;
 import android.util.FloatMath;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
 import android.widget.ImageView;
 public class TouchImageView extends ImageView
 {
   private static final String TAG = "Touch";
   Matrix matrix = new Matrix();
   Matrix savedMatrix = new Matrix();
   // We can be in one of these 3 states
   static final int NONE = 0;
   static final int DRAG = 1;
   static final int ZOOM = 2;
   int mode = NONE;
   // Remember some things for zooming
   PointF start = new PointF();
   PointF mid = new PointF();
   float oldDist = 1f;
   Context context;
   public TouchImageView(Context context)
   {
     super(context);
     super.setClickable(true);
     this.context = context;
     matrix.setTranslate(1f, 1f);
     setImageMatrix(matrix);
     setScaleType(ScaleType.MATRIX);
     setOnTouchListener(new OnTouchListener()
     {
       @Override
       public boolean onTouch(View v, MotionEvent rawEvent)
       {
         WrapMotionEvent event = WrapMotionEvent.wrap(rawEvent);
         // Dump touch event to log
         // if (Viewer.isDebug == true)
         {
           // dumpEvent(event);
           //
         }
         // Handle touch events here...
         switch (event.getAction() & MotionEvent.ACTION_MASK)
         {
           case MotionEvent.ACTION_DOWN:
           savedMatrix.set(matrix);
           start.set(event.getX(), event.getY());
           Log.d(TAG, "mode=DRAG");
           mode = DRAG;
           break;
           case MotionEvent.ACTION_POINTER_DOWN:
           oldDist = spacing(event);
           Log.d(TAG, "oldDist=" + oldDist);
           if (oldDist > 10f)
           {
             savedMatrix.set(matrix);
             midPoint(mid, event);
             mode = ZOOM;
             Log.d(TAG, "mode=ZOOM");
           }
           break;
           case MotionEvent.ACTION_UP:
           int xDiff = (int) Math.abs(event.getX() - start.x);
           int yDiff = (int) Math.abs(event.getY() - start.y);
           if (xDiff < 8 && yDiff < 8)
           {
             performClick();
           }
           case MotionEvent.ACTION_POINTER_UP:
           mode = NONE;
           Log.d(TAG, "mode=NONE");
           break;
           case MotionEvent.ACTION_MOVE:
           if (mode == DRAG)
           {
             // ...
             matrix.set(savedMatrix);
             matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
           }
           else if (mode == ZOOM)
           {
             float newDist = spacing(event);
             Log.d(TAG, "newDist=" + newDist);
             if (newDist > 10f)
             {
               matrix.set(savedMatrix);
               float scale = newDist / oldDist;
               matrix.postScale(scale, scale, mid.x, mid.y);
             }
           }
           break;
         }
         setImageMatrix(matrix);
         return true; // indicate event was handled
       }
     }
     );
   }
   public void setImage(Bitmap bm, int displayWidth, int displayHeight)
   {
     super.setImageBitmap(bm);
     //Fit to screen.
     float scale;
     if ((displayHeight / bm.getHeight()) >= (displayWidth / bm.getWidth()))
     {
       scale = (float)displayWidth / (float)bm.getWidth();
     }
     else
     {
       scale = (float)displayHeight / (float)bm.getHeight();
     }
     savedMatrix.set(matrix);
     matrix.set(savedMatrix);
     matrix.postScale(scale, scale, mid.x, mid.y);
     setImageMatrix(matrix);
     // Center the image
     float redundantYSpace = (float)displayHeight - (scale * (float)bm.getHeight()) ;
     float redundantXSpace = (float)displayWidth - (scale * (float)bm.getWidth());
     redundantYSpace /= (float)2;
     redundantXSpace /= (float)2;
     savedMatrix.set(matrix);
     matrix.set(savedMatrix);
     matrix.postTranslate(redundantXSpace, redundantYSpace);
     setImageMatrix(matrix);
   }
   /** Show an event in the LogCat view, for debugging */
   @SuppressWarnings("unused")
   private void dumpEvent(WrapMotionEvent event)
   {
     String names[] =
     {
       "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",
       "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?"
     }
     ;
     StringBuilder sb = new StringBuilder();
     int action = event.getAction();
     int actionCode = action & MotionEvent.ACTION_MASK;
     sb.append("event ACTION_").append(names[actionCode]);
     if (actionCode == MotionEvent.ACTION_POINTER_DOWN
     || actionCode == MotionEvent.ACTION_POINTER_UP)
     {
       sb.append("(pid ").append(
       action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
       sb.append(")");
     }
     sb.append("[");
     for (int i = 0; i < event.getPointerCount(); i++)
     {
       sb.append("#").append(i);
       sb.append("(pid ").append(event.getPointerId(i));
       sb.append(")=").append((int) event.getX(i));
       sb.append(",").append((int) event.getY(i));
       if (i + 1 < event.getPointerCount())
       sb.append(";");
     }
     sb.append("]");
     Log.d(TAG, sb.toString());
   }
   /** Determine the space between the first two fingers */
   private float spacing(WrapMotionEvent event)
   {
     float x = event.getX(0) - event.getX(1);
     float y = event.getY(0) - event.getY(1);
     return FloatMath.sqrt(x * x + y * y);
   }
   /** Calculate the mid point of the first two fingers */
   private void midPoint(PointF point, WrapMotionEvent event)
   {
     float x = event.getX(0) + event.getX(1);
     float y = event.getY(0) + event.getY(1);
     point.set(x / 2, y / 2);
   }
 }


Motion class to help in touch event


 package com.ahmad;
 import android.view.MotionEvent;
 public class EclairMotionEvent extends WrapMotionEvent {
   protected EclairMotionEvent(MotionEvent event) {
       super(event);
   }
   public float getX(int pointerIndex) {
       return event.getX(pointerIndex);
   }
   public float getY(int pointerIndex) {
       return event.getY(pointerIndex);
   }
   public int getPointerCount() {
       return event.getPointerCount();
   }
   public int getPointerId(int pointerIndex) {
       return event.getPointerId(pointerIndex);
   }
 }

Class to keep information about Pointer ID

 package com.ahmad;
 import android.view.MotionEvent;
 public class WrapMotionEvent {
  protected MotionEvent event;
  protected WrapMotionEvent(MotionEvent event) {
  this.event = event;
  }
    static public WrapMotionEvent wrap(MotionEvent event) {
  try {
   return new EclairMotionEvent(event);
  } catch (VerifyError e) {
   return new WrapMotionEvent(event);
  }
  }
  public int getAction() {
  return event.getAction();
  }
  public float getX() {
  return event.getX();
  }
  public float getX(int pointerIndex) {
  verifyPointerIndex(pointerIndex);
  return getX();
  }
  public float getY() {
  return event.getY();
  }
  public float getY(int pointerIndex) {
  verifyPointerIndex(pointerIndex);
  return getY();
  }
  public int getPointerCount() {
  return 1;
  }
  public int getPointerId(int pointerIndex) {
  verifyPointerIndex(pointerIndex);
  return 0;
  }
  private void verifyPointerIndex(int pointerIndex) {
  if (pointerIndex > 0) {
   throw new IllegalArgumentException(
    "Invalid pointer index for Donut/Cupcake");
  }
  }
 }