title: zooming an image view android
body: <p>I'm developing a program to guide students in my college to go around the building. The only problem now is with zooming. I tried this code to zoom in and out an image view and it is working but the only problem is that I want it to stop zooming out in a certain place or to stop at the original image size </p>
  
  <pre><code>private static final String TAG = "Touch";
      @SuppressWarnings("unused")
      private static final float MIN_ZOOM = 1f,MAX_ZOOM = 1f;
  
      // These matrices will be used to scale points of the image
      Matrix matrix = new Matrix();
      Matrix savedMatrix = new Matrix();
  
      // The 3 states (events) which the user is trying to perform
      static final int NONE = 0;
      static final int DRAG = 1;
      static final int ZOOM = 2;
      int mode = NONE;
  
      // these PointF objects are used to record the point(s) the user is touching
      PointF start = new PointF();
      PointF mid = new PointF();
      float oldDist = 1f;
  
  
  
      /** Called when the activity is first created. */
      @Override
      public void onCreate(Bundle savedInstanceState) 
      {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.ground_layout);
          ImageView view = (ImageView) findViewById(R.id.gf);
          view.setOnTouchListener(this);
  
  
  
  
  
      }
  
  
      public boolean onTouch(View v, MotionEvent event) 
      {
          ImageView view = (ImageView) v;
          view.setScaleType(ImageView.ScaleType.MATRIX);
          float scale;
  
          dumpEvent(event);
          // Handle touch events here...
  
          switch (event.getAction() &amp; MotionEvent.ACTION_MASK) 
          {
              case MotionEvent.ACTION_DOWN:   // first finger down only
                                                  savedMatrix.set(matrix);
                                                  start.set(event.getX(), event.getY());
                                                  Log.d(TAG, "mode=DRAG"); // write to LogCat
                                                  mode = DRAG;
                                                  break;
  
              case MotionEvent.ACTION_UP: // first finger lifted
  
              case MotionEvent.ACTION_POINTER_UP: // second finger lifted
  
                                                  mode = NONE;
                                                  Log.d(TAG, "mode=NONE");
                                                  break;
  
              case MotionEvent.ACTION_POINTER_DOWN: // first and second finger down
  
                                                  oldDist = spacing(event);
                                                  Log.d(TAG, "oldDist=" + oldDist);
                                                  if (oldDist &gt; 5f) {
                                                      savedMatrix.set(matrix);
                                                      midPoint(mid, event);
                                                      mode = ZOOM;
                                                      Log.d(TAG, "mode=ZOOM");
                                                  }
                                                  break;
  
              case MotionEvent.ACTION_MOVE:
  
                                                  if (mode == DRAG) 
                                                  { 
                                                      matrix.set(savedMatrix);
                                                      matrix.postTranslate(event.getX() - start.x, event.getY() - start.y); // create the transformation in the matrix  of points
                                                  } 
                                                  else if (mode == ZOOM) 
                                                  { 
                                                      // pinch zooming
                                                      float newDist = spacing(event);
                                                      Log.d(TAG, "newDist=" + newDist);
                                                      if (newDist &gt; 5f) 
                                                      {
                                                          matrix.set(savedMatrix);
                                                          scale = newDist / oldDist; // setting the scaling of the
                                                                                      // matrix...if scale &gt; 1 means
                                                                                      // zoom in...if scale &lt; 1 means
                                                                                      // zoom out
                                                          matrix.postScale(scale, scale, mid.x, mid.y);
                                                      }
                                                  }
                                                  break;
          }
  
          view.setImageMatrix(matrix); // display the transformation on screen
  
          return true; // indicate event was handled
      }
  
      /*
       * --------------------------------------------------------------------------
       * Method: spacing Parameters: MotionEvent Returns: float Description:
       * checks the spacing between the two fingers on touch
       * ----------------------------------------------------
       */
  
      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);
      }
  
      /*
       * --------------------------------------------------------------------------
       * Method: midPoint Parameters: PointF object, MotionEvent Returns: void
       * Description: calculates the midpoint between the two fingers
       * ------------------------------------------------------------
       */
  
      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);
      }
  
      /** Show an event in the LogCat view, for debugging */
      private void dumpEvent(MotionEvent 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 &amp; 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 &gt;&gt; MotionEvent.ACTION_POINTER_ID_SHIFT);
              sb.append(")");
          }
  
          sb.append("[");
          for (int i = 0; i &lt; 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 &lt; event.getPointerCount())
                  sb.append(";");
          }
  
          sb.append("]");
          Log.d("Touch Events ---------", sb.toString());
      }
  
  
  }
  </code></pre>