Android控件拖拽后页面刷新回来原始位置问题

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前言

在工作中遇到了这个问题,拖动一个图片按钮，切换页面后发现按钮又回到了原始的位置.

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一、解决思路

百度了下大致方法多为一种,即通过重写onTouchEvent()记录前后移动的相对坐标,然后根据相对坐标设置控件位置

二、使用步骤

1.拖动示例

代码如下（示例）：

        @Override
        public boolean onTouch(View view, MotionEvent event) {
            //得到事件的坐标
            int eventX = (int) event.getRawX();
            int eventY = (int) event.getRawY();
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    //得到父视图的right/bottom
                    if (maxRight == 0) {//保证只赋一次值
                        maxRight = parentView.getRight();
                        maxBottom = parentView.getBottom();
                    }
                    //第一次记录lastX/lastY
                    lastX = eventX;
                    lastY = eventY;
                    isMove = false;
                    downTime = System.currentTimeMillis();
                    if (haveDelay()) {
                        canDrag = false;
                    } else {
                        canDrag = true;
                    }
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (haveDelay() && !canDrag) {
                        long currMillis = System.currentTimeMillis();
                        if (currMillis - downTime >= delay) {
                            canDrag = true;
                        }
                    }
                    if (!canDrag) {
                        break;
                    }
                    //计算事件的偏移
                    int dx = eventX - lastX;
                    int dy = eventY - lastY;
                    if (dx != 0 && dy != 0) {
                        //根据事件的偏移来移动imageView
                        int left = view.getLeft() + dx;
                        int top = view.getTop() + dy;
                        int right = view.getRight() + dx;
                        int bottom = view.getBottom() + dy;
                        //限制left  >=0
                        if (left < 0) {
                            right += -left;
                            left = 0;
                        }
                        //限制top
                        if (top < 0) {
                            bottom += -top;
                            top = 0;
                        }
                        //限制right <=maxRight
                        if (right > maxRight) {
                            left -= right - maxRight;
                            right = maxRight;
                        }
                        //限制bottom <=maxBottom
                        if (bottom > maxBottom) {
                            top -= bottom - maxBottom;
                            bottom = maxBottom;
                        }
                        //不要这么设置View.layout(int left,int top,int right,int bottom)方法
//                        view.setLeft(left);
//                        view.setTop(top);
//                        view.setRight(right);
//                        view.setBottom(bottom);
                         //要用setLayoutParams这么设置
                        setViewLocation(view, left, top, right, bottom);
                        //再次记录lastX/lastY
                        lastX = eventX;
                        lastY = eventY;
                        isMove = true;
                    }
                    break;
                default:
                    break;
            }
            return isMove;
        }
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2.方法示例

代码如下（示例）：

    private static void setViewLocation(View view, int left, int top, int right, int bottom) {
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(right - left, bottom - top);
        params.addRule(RelativeLayout.ALIGN_PARENT_LEFT, RelativeLayout.TRUE);
        params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);
        params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE);
        params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
        ViewParent parent = view.getParent();
        View p = (View) parent;
        int marginRight = p.getWidth() - right;
        int marginBottom = p.getHeight() - bottom;
        params.setMargins(left, top, marginRight, marginBottom);
        view.setLayoutParams(params);
    }

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总结

以上就是今天要讲的内容，本文主要实现ImageView拖拽时限制区域及解决切换页面时ImageView位置重置问题。