通過手勢進行圖片的縮放，在onTouch事件中，MotionEvent.ACTION_POINTER_DOWN觸發時則代表是多點觸控，可以通過兩點縮放的距離來縮放圖片。
當圖片加載完成時設置圖片居中，默認大小爲屏幕的80%，主要代碼如下：
private void setTreeObserver() {
viewTreeObserver = p_w_picpath.getViewTreeObserver();
viewTreeObserver.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
if (state_height == 0) {
Rect frame = new Rect();
getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
state_height = frame.top;
startScale(bm);
center();
p_w_picpath.setImageMatrix(matrix);
p_w_picpath.setOnTouchListener(MainActivity.this);
}
}
});
}設置屏幕點擊事件：
@Override
public boolean onTouch(View v, MotionEvent event) {
try {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
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);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break;
}
p_w_picpath.setImageMatrix(matrix);
CheckScale();
center();
return true;
} catch (Exception ex) {
return false;
}
}