title: Add limit to zoom-in and zoom-out in android
body: <p>I have an imageview that can be zoomed. I have a code that works well, but my problem is that I want to add a limit for maximum and minimum zooming levels.</p>
  
  <pre><code>import android.annotation.TargetApi;
  import android.app.ActionBar;
  import android.app.Activity;
  import android.graphics.Matrix;
  import android.graphics.PointF;
  import android.os.Build;
  import android.os.Bundle;
  import android.util.FloatMath;
  import android.util.Log;
  import android.view.MenuItem;
  import android.view.MotionEvent;
  import android.view.View;
  import android.view.View.OnTouchListener;
  import android.widget.ImageView;
  
  @TargetApi(Build.VERSION_CODES.HONEYCOMB)
  public class Reach extends Activity implements OnTouchListener
  {
      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;
  
  @Override
  protected void onCreate(Bundle savedInstanceState)
  {
      // TODO Auto-generated method stub
      super.onCreate(savedInstanceState);
      setContentView(R.layout.reach_us);
      int currentAPIVersion = android.os.Build.VERSION.SDK_INT;
  
      if (currentAPIVersion &gt;= android.os.Build.VERSION_CODES.HONEYCOMB) 
      {
  
          // RUN THE CODE SPECIFIC TO THE API LEVELS ABOVE HONEYCOMB (API 11+)   
          ActionBar actionBar = getActionBar();
          actionBar.setDisplayHomeAsUpEnabled(true);
      }
      ImageView view=(ImageView)findViewById(R.id.map);
      view.setOnTouchListener(this);
  }
  
  @Override
  public boolean onOptionsItemSelected(MenuItem item)
  {
  
      switch (item.getItemId()) {
  
      case android.R.id.home: {
          this.finish();
  
          return true;
      }
  
      default:
          return super.onOptionsItemSelected(item);
      }
  }
  @Override
  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>
  
  <p>I have seen lot of question &amp; answers linked with this, but no one really helps me. Please give me a solution. Thanks in advance</p>