Android实现对imageview的拖动以及缩放

package org.wch.gesture; import android.graphics.Matrix; import android.graphics.PointF; import android.util.FloatMath; import android.util.Log; 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 { Matrix matrix = new Matrix(); Matrix savedMatrix = new Matrix(); public ImageView image; static final int NONE = 0; static final int DRAG = 1; static final int ZOOM = 2; int mode = NONE; 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; // dumpEvent(event); switch (event.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: Log.w("FLAG", "ACTION_DOWN"); matrix.set(view.getImageMatrix()); savedMatrix.set(matrix); start.set(event.getX(), event.getY()); mode = DRAG; break; case MotionEvent.ACTION_POINTER_DOWN: Log.w("FLAG", "ACTION_POINTER_DOWN"); oldDist = spacing(event); if (oldDist > 10f) { savedMatrix.set(matrix); midPoint(mid, event); mode = ZOOM; } break; case MotionEvent.ACTION_UP: Log.w("FLAG", "ACTION_UP"); case MotionEvent.ACTION_POINTER_UP: Log.w("FLAG", "ACTION_POINTER_UP"); mode = NONE; break; case MotionEvent.ACTION_MOVE: Log.w("FLAG", "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); if (newDist > 10f) { matrix.set(savedMatrix); float scale = newDist / oldDist; matrix.postScale(scale, scale, mid.x, mid.y); } } break; } view.setImageMatrix(matrix); return true; } 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); } }