DragView（一）

传承者（Inheritors）打造共同进步生态圈！！！

转载：
http://blog.youkuaiyun.com/lmj623565791/article/details/46858663；

三段论：
思考，自定义，使用

public class CustomViewGroup2 extends LinearLayout {

    private ViewDragHelper mViewDragHelper;

    public CustomViewGroup2(Context context) {
        this(context,null);
    }
    public CustomViewGroup2(Context context, AttributeSet attrs) {
        super(context, attrs);
        mViewDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {
            @Override
            public boolean tryCaptureView(View child, int pointerId) {
                return true;
            }

            @Override
            public int clampViewPositionHorizontal(View child, int left, int dx) {

              final  int leftBound = getPaddingLeft();
                final int rightBound = getWidth()-child.getWidth()-leftBound;

                final int mewLeft = Math.min(Math.max(left,leftBound),rightBound);

                return mewLeft;
            }

            @Override
            public int clampViewPositionVertical(View child, int top, int dy) {
                return top;
            }
        });
    }


    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        return mViewDragHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        mViewDragHelper.processTouchEvent(event);

        return true;
    }
}

调用

<?xml version="1.0" encoding="utf-8"?>
<com.example.administrator.testapplication.CustomViewGroup2 xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_margin="10dp"
        android:gravity="center"
        android:layout_gravity="center"
        android:background="#44ff0000"
        android:text="I can be dragged !"
        android:layout_width="100dp"
        android:layout_height="100dp"/>

    <TextView
        android:layout_margin="10dp"
        android:layout_gravity="center"
        android:gravity="center"
        android:background="#44ff0000"
        android:text="I can be dragged !"
        android:layout_width="100dp"
        android:layout_height="100dp"/>

    <TextView
        android:layout_margin="10dp"
        android:layout_gravity="center"
        android:gravity="center"
        android:background="#44ff0000"
        android:text="I can be dragged !"
        android:layout_width="100dp"
        android:layout_height="100dp"/>

</com.example.administrator.testapplication.CustomViewGroup2>

部分方法解释

  /**
         * Restrict the motion of the dragged child view along the horizontal axis.
         * The default implementation does not allow horizontal motion; the extending
         * class must override this method and provide the desired clamping.
         *
         *
         * @param child Child view being dragged
         * @param left Attempted motion along the X axis
         * @param dx Proposed change in position for left
         * @return The new clamped position for left
         */
        public int clampViewPositionHorizontal(View child, int left, int dx) {
            return 0;
        }


  /**
         * Restrict the motion of the dragged child view along the vertical axis.
         * The default implementation does not allow vertical motion; the extending
         * class must override this method and provide the desired clamping.
         *
         *
         * @param child Child view being dragged
         * @param top Attempted motion along the Y axis
         * @param dy Proposed change in position for top
         * @return The new clamped position for top
         */
        public int clampViewPositionVertical(View child, int top, int dy) {
            return 0;
        }

效果：