Restricting panning and zooming
<p>Hi I’m trying to create an application where you can zoom and pan around a campus site map. I have that working but have run into problems restricting how much you can pan and zoom.I need help setting panning and zooming boundaries.<br>
Any help would be greatly appreciated,</p>

<p>Thanks in advance<br>
Here’s the code.  </p>

<pre><code>package com.scott;

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;

public class Touch extends Activity implements OnTouchListener,OnClickListener {
   private static final String TAG = "Touch";

   Matrix matrix = new Matrix();
   Matrix savedMatrix = new Matrix();
   static final int NONE = 0;
   static final int DRAG = 1;
   static final int ZOOM = 2;
   int mode = NONE;

   PointF start = new PointF();
   PointF mid = new PointF();
   float oldDist = 1f;

   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.touch);
      ImageView view = (ImageView) findViewById(R.id.imageView);
      view.setOnTouchListener(this);

     Button buttonClose =(Button)findViewById(R.id.buttonClose);
     buttonClose.setOnClickListener(this); 

   }

   @Override
   public boolean onTouch(View v, MotionEvent event) {
      ImageView view = (ImageView) v;


      dumpEvent(event);

      switch (event.getAction() &amp; 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 &gt; 10f) {
            savedMatrix.set(matrix);
            midPoint(mid, event);
            mode = ZOOM;
            Log.d(TAG, "mode=ZOOM");
         }
         break;
      case MotionEvent.ACTION_UP:
      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 &gt; 10f) {
               matrix.set(savedMatrix);
               float scale = newDist / oldDist;
               matrix.postScale(scale, scale, mid.x, mid.y);
            }
         }
         break;
      }

      view.setImageMatrix(matrix);
      return true; 
   }

   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(TAG, sb.toString());
   }

   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);
   }

@Override
public void onClick(View src) {
    switch(src.getId()){ 
    case R.id.buttonClose:
        finish(); 
        break; 

    }   
    }
}
</code></pre>
