多点触摸放大图片的自定义listener

可以看到很多相册应用，通过两根手指的操作，能让图片放大缩小。很简单，通过自定义的继承于onTouchListener的类，去实现这样的效果。代码如下：

package cn.test;

import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;

public class MulitPointTouchListener implements OnTouchListener {

    // These matrices will be used to move and zoom image
    Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();

    public ImageView image;
    // 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;

    
    public MulitPointTouchListener(ImageView image) {
  super();
  this.image = image;
 }

 @Override
    public boolean onTouch(View v, MotionEvent event) {
  this.image.setScaleType(ScaleType.MATRIX);

            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;

                    /*
                     * float scaleWidth=180f/320; float scaleHeight=240f/480;
                     * matrix.reset(); matrix.postScale(scaleWidth, scaleHeight);
                     */
                    //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());
    }

    /** Determine the space between the first two fingers */
    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);
    }

    /** Calculate the mid point of the first 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);
    }
}

评论

1 楼 xunhuan01 2012-04-11  

view.getImageMatrix()， savedMatrix.set(matrix);  这两句是什么意思？
为什么是event.getx()-start.x,event.gety()-start.y