可以拖拽的ViewGroup，仿微信拖拽縮放關閉

此處利用了ViewDragHelper類

內部設置了一個監聽，鬆手進行關閉即可

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.FrameLayout;

public class DragViewGrouop extends FrameLayout {

    private ViewDragHelper dragHelper;
    private int mOldLeft;
    private int mOldTop;
    private int mHeight;
    private float mScaleValue;
    private float mMinRate = 0.4f;

    public DragViewGrouop(@NonNull Context context) {
        this(context, null);
    }

    public DragViewGrouop(@NonNull Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public DragViewGrouop(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr, 0);
        init();
    }

    private void init() {
        dragHelper = ViewDragHelper.create(this, new ViewDragHelper.Callback() {
            @Override
            public boolean tryCaptureView(View child, int pointerId) {
                return true;
            }

            @Override
            public void onViewReleased(View releasedChild, float xvel, float yvel) {
                if (dragListener != null && mScaleValue < mMinRate) {
                    dragListener.onViewReleased();
                } else {
                    dragHelper.settleCapturedViewAt(mOldLeft, mOldTop);
                    invalidate();
                    ViewCompat.animate(releasedChild).scaleX(1).setDuration(0);
                }
            }

            @Override
            public void onViewCaptured(View capturedChild, int activePointerId) {
                mOldLeft = capturedChild.getLeft();
                mOldTop = capturedChild.getTop();
            }

            @Override
            public int clampViewPositionVertical(View child, int top, int dy) {
                mScaleValue = 1.00f - Math.abs((top - mOldTop) * 1.0f / (mHeight - mOldTop));
                ViewCompat.animate(child).scaleX(mScaleValue).setDuration(0);
                return top;
            }

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

    @Override
    public void computeScroll() {
        super.computeScroll();
        if (dragHelper != null && dragHelper.continueSettling(true)) {
            invalidate();
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mHeight = h;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (dragHelper != null) {
            return dragHelper.shouldInterceptTouchEvent(ev);
        }
        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (dragHelper != null) {
            dragHelper.processTouchEvent(event);
        }
        return true;
    }

    private DragListener dragListener;

    public void setOnDragListener(DragListener dragListener) {
        this.dragListener = dragListener;
    }

    public interface DragListener {
        void onViewReleased();
    }