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); }} 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