Android-自定义纵向拽托关闭布局

效果

代码实现

/**
 * 上下拽托移动布局
 */
public class VerticalDragLayout extends FrameLayout {
    /**
     * 触发阈值
     */
    private static final float TRIGGER_THRESHOLD_VALUE = 0.75f;

    private ViewDragHelper mViewDragHelper;

    /**
     * 唯一内容子View
     */
    private View mContentView;
    /**
     * 当前内容子View的Top值，由于子View引起重绘或addView引起重绘会导致requestLayout()，会重新onLayout()子View
     * 而layout子View，要在onLayout中处理。如果在onViewPositionChanged()中单独onLayout，并且又没有保存top值为成员变量，就会因为其他原因引起的requestLayout()
     * 导致子View的top值默认值为0，会突然抖回顶部
     */
    private int mCurrentTop = 0;
    /**
     * 是否已关闭
     */
    private boolean isClosed = true;
    /**
     * 拽托状态回调
     */
    private OnDragStateChangeListener mOnDragStateChangeListener;

    public VerticalDragLayout(Context context) {
        super(context);
        init();
    }

    public VerticalDragLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public VerticalDragLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mViewDragHelper = ViewDragHelper.create(this, 0.5f, new ViewDragHelperCallBack());
    }

    private class ViewDragHelperCallBack extends ViewDragHelper.Callback {
        /**
         * 开始拽托时的X坐标
         */
        private int mDownX;
        /**
         * 开始拽托时的Y坐标
         */
        private int mDownY;

        @Override
        public boolean tryCaptureView(@NonNull View child, int pointerId) {
            //返回ture则表示可以捕获该view，手指摸上一瞬间调用
            return child == mContentView;
        }

        @Override
        public void onViewCaptured(@NonNull View capturedChild, int activePointerId) {
            super.onViewCaptured(capturedChild, activePointerId);
            mDownX = capturedChild.getLeft();
            mDownY = capturedChild.getTop();
        }

        @Override
        public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
            //手指触摸移动时实时回调, top表示要到的y位置
            //限制只能向下滑
            if (top < 0) {
                return 0;
            }
            //最多只能滑动到内容View的高度
            int maxTop = mContentView.getHeight();
            return Math.min(top, maxTop);
        }

        @Override
        public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
            //手指释放时回调
            int finalLeft = releasedChild.getLeft();
            final int currentLeft = releasedChild.getLeft();
            final int currentTop = releasedChild.getTop();
            //最小移动距离
            int minMoveDistance = releasedChild.getHeight() / 3;
            //计算移动距离
            int distanceX = currentLeft - mDownX;
            int distanceY = currentTop - mDownY;
            //滚动到顶部
            Runnable scrollToTop = new Runnable() {
                @Override
                public void run() {
                    mViewDragHelper.settleCapturedViewAt(finalLeft, 0);
                }
            };
            //滚动到底部
            Runnable scrollToBottom = new Runnable() {
                @Override
                public void run() {
                    int finalTop = releasedChild.getHeight();
                    mViewDragHelper.settleCapturedViewAt(finalLeft, finalTop);
                }
            };
            //根据移动距离占总大小的百分比，决定滚动到顶部还是底部
            Runnable scrollByDistancePercentage = new Runnable() {
                @Override
                public void run() {
                    //当前已移动距离的百分比值
                    float movePercentage = (releasedChild.getTop() * 1f) / releasedChild.getHeight();
                    //剩余的内容占的百分比
                    float remainDistancePercentage = 1f - movePercentage;
                    //剩余的内容，小于阈值，则移动到底部
                    if (remainDistancePercentage <= TRIGGER_THRESHOLD_VALUE) {
                        scrollToBottom.run();
                    } else {
                        //小于阈值，回弹回顶部
                        scrollToTop.run();
                    }
                }
            };
            //判断是否是上下滑，左右滑不需要动
            if (Math.abs(distanceY) > Math.abs(distanceX)) {
                //上下滑，滑动得少，并且速度很快，则为fling操作
                if (Math.abs(distanceY) < minMoveDistance && Math.abs(yvel) > Math.abs(mViewDragHelper.getMinVelocity())) {
                    //距离相减为正数，并且惯性速度为正数（如果先下滑，再回去，速度值会为负），则为往下滑
                    if (distanceY > 0 && yvel > 0) {
                        scrollToBottom.run();
                    } else {
                        //否则为向上滑
                        scrollToTop.run();
                    }
                } else {
                    //不是fling操作，根据移动距离占总大小的百分比，决定滚动到顶部还是底部
                    scrollByDistancePercentage.run();
                }
            }
            invalidate();
        }

        @Override
        public void onViewPositionChanged(@NonNull View changedView, int left, int top, int dx, int dy) {
            mCurrentTop = top;
            //统一在onLayout中，重新布局子View位置，来移动子View
            requestLayout();
        }

        @Override
        public int getViewVerticalDragRange(@NonNull View child) {
            if (mContentView == null) {
                return 0;
            }
            if (mContentView == child) {
                return mContentView.getHeight();
            } else {
                return 0;
            }
        }

        @Override
        public void onViewDragStateChanged(int state) {
            super.onViewDragStateChanged(state);
            if (state == ViewDragHelper.STATE_DRAGGING) {
                if (mOnDragStateChangeListener != null) {
                    mOnDragStateChangeListener.onStartDrag();
                }
            } else if (state == ViewDragHelper.STATE_IDLE) {
                if (mOnDragStateChangeListener != null) {
                    mOnDragStateChangeListener.onStopDrag();
                }
                isClosed = (mContentView.getTop() == mContentView.getHeight());
                if (isClosed) {
                    if (mOnDragStateChangeListener != null) {
                        mOnDragStateChangeListener.onDragToBottom();
                    }
                }
            }
        }
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        //移动内容子View
        MarginLayoutParams params = (MarginLayoutParams) mContentView.getLayoutParams();
        mContentView.layout(
                params.leftMargin,
                mCurrentTop + params.topMargin,
                mContentView.getMeasuredWidth() + params.leftMargin,
                mCurrentTop + mContentView.getMeasuredHeight() + params.topMargin
        );
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        int childCount = getChildCount();
        if (childCount != 1) {
            throw new RuntimeException("子View必须只有1个，就是内容View");
        }
        mContentView = getChildAt(0);
    }

    @Override
    public void computeScroll() {
        if (mViewDragHelper.continueSettling(true)) {
            ViewCompat.postInvalidateOnAnimation(this);
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        //将onInterceptTouchEvent委托给ViewDragHelper
        return mViewDragHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //将onTouchEvent委托给ViewDragHelper
        mViewDragHelper.processTouchEvent(event);
        return true;
    }

    public boolean isClosed() {
        return isClosed;
    }

    /**
     * 结束回调
     */
    public interface OnDragStateChangeListener {
        void onStartDrag();

        void onStopDrag();

        void onDragToBottom();
    }

    public void setOnDragStateChangeListener(OnDragStateChangeListener listener) {
        this.mOnDragStateChangeListener = listener;
    }
}

使用

• 布局xml

<com.psy1.cosleep.library.view.VerticalDragLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:id="@+id/vertical_drag_layout"
  android:layout_width="match_parent"
  android:layout_height="match_parent">

  //....

</com.psy1.cosleep.library.view.VerticalDragLayout>

• Java代码

VerticalDragLayout verticalDragLayout = findViewById(R.id.vertical_drag_layout);
verticalDragLayout.setOnDragStateChangeListener(new VerticalDragLayout.OnDragStateChangeListener() {
  @Override
  public void onStartDrag() {
    //开始拽托
  }

  @Override
  public void onStopDrag() {
    //停止拽托
  }

  @Override
  public void onDragToBottom() {
    //拽托到底部，可关闭页面
  }
});