本文推出了两种Android手势实现ImageView缩放图片大小的方法，分享给大家供大家参考，具体内容如下

方法一：
将以下代码写到MulitPointTouchListener.java中，然后对你相应的图片进行OnTouchListener。
例如：imageView.setOnTouchListener(new MulitPointTouchListener ());
在xml中要将ImageView的缩放格式改成Matrix
例如：android:scaleType="matrix"
这样就可以实现图片的缩放了
下面是MulitPointTouchListener.java代码：

public class MulitPointTouchListener implements OnTouchListener {  
    private static final String TAG = "Touch";  
    // These matrices will be used to move and zoom image  
    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;  
 
    @Override 
    public boolean onTouch(View v, MotionEvent event) {  
 
        ImageView view = (ImageView) v;  
        // Log.e("view_width",  
        // view.getImageMatrix()..toString()+"*"+v.getWidth());  
        // Dump touch event to log  
        dumpEvent(event);  
 
        // Handle touch events here...  
        switch (event.getAction() & MotionEvent.ACTION_MASK) {  
        case MotionEvent.ACTION_DOWN:  
 
            matrix.set(view.getImageMatrix());  
            savedMatrix.set(matrix);  
            start.set(event.getX(), event.getY());  
            //Log.d(TAG, "mode=DRAG");  
            mode = DRAG;  
 
             
            //Log.d(TAG, "mode=NONE");  
            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:  
        case MotionEvent.ACTION_POINTER_UP:  
            mode = NONE;  
            //Log.e("view.getWidth", view.getWidth() + "");  
            //Log.e("view.getHeight", view.getHeight() + "");  
 
            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;  
        }  
 
        view.setImageMatrix(matrix);  
        return true; // indicate event was handled  
    }  
 
    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 & 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());  
    }  
 
     
    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);  
    }  
} 

方法二：自定义一个ImageView，例如TouchImageView：

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;

public class TouchImageView extends ImageView {

  Matrix 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 last = new PointF();
  PointF start = new PointF();
  float minScale = 1f;
  float maxScale = 3f;
  float[] m;


  int viewWidth, viewHeight;
  static final int CLICK = 3;
  float saveScale = 1f;
  protected float origWidth, origHeight;
  int oldMeasuredWidth, oldMeasuredHeight;


  ScaleGestureDetector mScaleDetector;

  Context context;

  public TouchImageView(Context context) {
    super(context);
    sharedConstructing(context);
  }

  public TouchImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
    sharedConstructing(context);
  }
  
  private void sharedConstructing(Context context) {
    super.setClickable(true);
    this.context = context;
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    matrix = new Matrix();
    m = new float[9];
    setImageMatrix(matrix);
    setScaleType(ScaleType.MATRIX);

    setOnTouchListener(new OnTouchListener() {

      @Override
      public boolean onTouch(View v, MotionEvent event) {
        mScaleDetector.onTouchEvent(event);
        PointF curr = new PointF(event.getX(), event.getY());

        switch (event.getAction()) {
          case MotionEvent.ACTION_DOWN:
           last.set(curr);
            start.set(last);
            mode = DRAG;
            break;
            
          case MotionEvent.ACTION_MOVE:
            if (mode == DRAG) {
              float deltaX = curr.x - last.x;
              float deltaY = curr.y - last.y;
              float fixTransX = getFixDragTrans(deltaX, viewWidth, origWidth * saveScale);
              float fixTransY = getFixDragTrans(deltaY, viewHeight, origHeight * saveScale);
              matrix.postTranslate(fixTransX, fixTransY);
              fixTrans();
              last.set(curr.x, curr.y);
            }
            break;

          case MotionEvent.ACTION_UP:
            mode = NONE;
            int xDiff = (int) Math.abs(curr.x - start.x);
            int yDiff = (int) Math.abs(curr.y - start.y);
            if (xDiff < CLICK && yDiff < CLICK)
              performClick();
            break;

          case MotionEvent.ACTION_POINTER_UP:
            mode = NONE;
            break;
        }
        
        setImageMatrix(matrix);
        invalidate();
        return true; // indicate event was handled
      }

    });
  }

  public void setMaxZoom(float x) {
    maxScale = x;
  }

  private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
      mode = ZOOM;
      return true;
    }

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
      float mScaleFactor = detector.getScaleFactor();
      float origScale = saveScale;
      saveScale *= mScaleFactor;
      if (saveScale > maxScale) {
        saveScale = maxScale;
        mScaleFactor = maxScale / origScale;
      } else if (saveScale < minScale) {
        saveScale = minScale;
        mScaleFactor = minScale / origScale;
      }

      if (origWidth * saveScale <= viewWidth || origHeight * saveScale <= viewHeight)
        matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2, viewHeight / 2);
      else
        matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY());

      fixTrans();
      return true;
    }
  }

  void fixTrans() {
    matrix.getValues(m);
    float transX = m[Matrix.MTRANS_X];
    float transY = m[Matrix.MTRANS_Y];
    
    float fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale);
    float fixTransY = getFixTrans(transY, viewHeight, origHeight * saveScale);

    if (fixTransX != 0 || fixTransY != 0)
      matrix.postTranslate(fixTransX, fixTransY);
  }

  float getFixTrans(float trans, float viewSize, float contentSize) {
    float minTrans, maxTrans;

    if (contentSize <= viewSize) {
      minTrans = 0;
      maxTrans = viewSize - contentSize;
    } else {
      minTrans = viewSize - contentSize;
      maxTrans = 0;
    }

    if (trans < minTrans)
      return -trans + minTrans;
    if (trans > maxTrans)
      return -trans + maxTrans;
    return 0;
  }
  
  float getFixDragTrans(float delta, float viewSize, float contentSize) {
    if (contentSize <= viewSize) {
      return 0;
    }
    return delta;
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    viewWidth = MeasureSpec.getSize(widthMeasureSpec);
    viewHeight = MeasureSpec.getSize(heightMeasureSpec);
    
    //
    // Rescales image on rotation
    //
    if (oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight
        || viewWidth == 0 || viewHeight == 0)
      return;
    oldMeasuredHeight = viewHeight;
    oldMeasuredWidth = viewWidth;

    if (saveScale == 1) {
      //Fit to screen.
      float scale;

      Drawable drawable = getDrawable();
      if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0)
        return;
      int bmWidth = drawable.getIntrinsicWidth();
      int bmHeight = drawable.getIntrinsicHeight();
      
      Log.d("bmSize", "bmWidth: " + bmWidth + " bmHeight : " + bmHeight);

      float scaleX = (float) viewWidth / (float) bmWidth;
      float scaleY = (float) viewHeight / (float) bmHeight;
      scale = Math.min(scaleX, scaleY);
      matrix.setScale(scale, scale);

      // Center the image
      float redundantYSpace = (float) viewHeight - (scale * (float) bmHeight);
      float redundantXSpace = (float) viewWidth - (scale * (float) bmWidth);
      redundantYSpace /= (float) 2;
      redundantXSpace /= (float) 2;

      matrix.postTranslate(redundantXSpace, redundantYSpace);

      origWidth = viewWidth - 2 * redundantXSpace;
      origHeight = viewHeight - 2 * redundantYSpace;
      setImageMatrix(matrix);
    }
    fixTrans();
  }
}

然后在我们的Activity中就可以直接使用了：

public class TouchImageViewActivity extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    TouchImageView img = (TouchImageView) findViewById(R.id.snoop);
    img.setImageResource(R.drawable.snoopy);
    img.setMaxZoom(4f);
  }
}