Android code to zoom an image in ImageView

 Java Code

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package com.example.calender;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

public class April extends Activity {
 ImageView imageDetail;
 Matrix matrix1 = new Matrix();
 Matrix savedMatrix = new Matrix();
 PointF startPoint = new PointF();
 PointF midPoint = new PointF();
 float oldDist = 1f;
 static final int NONE = 0;
 static final int DRAG = 1;
 static final int ZOOM = 2;
 int mode = NONE;

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.april);
  imageDetail = (ImageView) findViewById(R.id.imageView1);
  /**
   * set on touch listner on image
   */
  imageDetail.setOnTouchListener(new View.OnTouchListener() {

   @Override
   public boolean onTouch(View v, MotionEvent event) {

    ImageView view = (ImageView) v;
    System.out.println("matrix=" + savedMatrix.toString());
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:

     savedMatrix.set(matrix1);
     startPoint.set(event.getX(), event.getY());
     mode = DRAG;
     break;

    case MotionEvent.ACTION_POINTER_DOWN:

     oldDist = spacing(event);

     if (oldDist > 10f) {
      savedMatrix.set(matrix1);
      midPoint(midPoint, event);
      mode = ZOOM;
     }
     break;

    case MotionEvent.ACTION_UP:

    case MotionEvent.ACTION_POINTER_UP:
     mode = NONE;

     break;

    case MotionEvent.ACTION_MOVE:
     if (mode == DRAG) {
      matrix1.set(savedMatrix);
      matrix1.postTranslate(event.getX() - startPoint.x,
        event.getY() - startPoint.y);
     } else if (mode == ZOOM) {
      float newDist = spacing(event);
      if (newDist > 10f) {
       matrix1.set(savedMatrix);
       float scale = newDist / oldDist;
       matrix1.postScale(scale, scale, midPoint.x, midPoint.y);
      }
     }
     break;

    }
    view.setImageMatrix(matrix1);

    return true;
   }

   @SuppressLint("FloatMath")
   private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
   }

   private void midPoint(PointF point, MotionEvent event) {
    float x = event.getX(0) + event.getX(1);
    float y = event.getY(0) + event.getY(1);
    point.set(x / 2, y / 2);
   }
  });

 }

}