实现可拖动控件

public class DragLayout extends RelativeLayout {

    private ViewDragHelper mDragger;

    private ViewDragHelper.Callback callback;

    private ImageView imageView;

    private String mTitle;

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
    }

    public DragLayout(Context context) {
        this(context, null);
    }

    public void setTitle(String title) {
        this.mTitle = title;
    }

    public DragLayout(final Context context, AttributeSet attrs) {
        super(context, attrs);
        callback = new DraggerCallBack();
        //第二个参数就是滑动灵敏度的意思 可以随意设置
        mDragger = ViewDragHelper.create(this, 1.0f, callback);
        imageView = new ImageView(getContext());
        imageView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                
            }
        });
        imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
//        imageView.setImageResource(R.drawable.core_service_news);
        imageView.setImageResource(R.mipmap.core_float_service);
        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        layoutParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
        layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        layoutParams.rightMargin = DensityUtils.dp2px(getContext(), 5);
        layoutParams.bottomMargin = DensityUtils.dp2px(getContext(), 210); //
        layoutParams.width = 125;  // 写死尺寸，保证不同机型大小一致，2019.12.16
        layoutParams.height = 150;
        addView(imageView, layoutParams);
    }

    class DraggerCallBack extends ViewDragHelper.Callback {

        //这个地方实际上函数返回值为true就代表可以滑动 为false 则不能滑动
        @Override
        public boolean tryCaptureView(View child, int pointerId) {
            return true;
        }

        @Override
        public int clampViewPositionHorizontal(View child, int left, int dx) {
            //取得左边界的坐标
            final int leftBound = getPaddingLeft();
            //取得右边界的坐标
            final int rightBound = getWidth() - child.getWidth() - leftBound;
            //这个地方的含义就是 如果left的值 在leftbound和rightBound之间 那么就返回left
            //如果left的值 比 leftbound还要小 那么就说明 超过了左边界 那我们只能返回给他左边界的值
            //如果left的值 比rightbound还要大 那么就说明 超过了右边界，那我们只能返回给他右边界的值
            return Math.min(Math.max(left, leftBound), rightBound);
        }

        //纵向的注释就不写了 自己体会
        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            final int topBound = getPaddingTop();
            final int bottomBound = getHeight() - child.getHeight() - topBound;
            return Math.min(Math.max(top, topBound), bottomBound);
        }

        @Override
        public int getViewHorizontalDragRange(View child) {
            return imageView == child ? child.getWidth() : 0;
        }

        @Override
        public int getViewVerticalDragRange(View child) {
            return imageView == child ? child.getHeight() : 0;
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        //决定是否拦截当前事件
        return mDragger.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //处理事件
        mDragger.processTouchEvent(event);
        return isTouchPointInView(imageView, event.getRawX(), event.getRawY());
    }

    //(x,y)是否在view的区域内
    private boolean isTouchPointInView(View view, float x, float y) {
        if (view == null) {
            return false;
        }
        int[] location = new int[2];
        view.getLocationOnScreen(location);
        int left = location[0];
        int top = location[1];
        int right = left + view.getMeasuredWidth();
        int bottom = top + view.getMeasuredHeight();
        //view.isClickable() &&
        if (y >= top && y <= bottom && x >= left
                && x <= right) {
            return true;
        }
        return false;
    }


}