Android中图片的放大和缩小源码

/**   *    * @author chrp   *   *图片 的放大  缩小    */    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);      }  }

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();      }  }