Flutter 類抽屜效果動畫實現。

效果：

豎向抽屜：

    

橫向抽屜：

實現思路

•  在STACK 容器裏建立3個頁面.
  具體代碼以下：

child: Stack(        
            children: <Widget>[        
             Container(            
               color: widget?.backgroundColor,             
               child: buildContent(),         
              ),        
            buildTop(),        
           buildRight(),        
        ],),複製代碼

•  經過監聽onVerticalDragUpdate和onHorizontalDragUpdate 獲取屬相和橫向滑動的座標信息

  onVerticalDragUpdate: _inContent
              ? (details) {
                  calculateOffsetY(
                      details,
                      ((widget?.topPopConfig?.topMaxHeight ?? 0) <= 0
                              ? _height
                              : (widget?.topPopConfig?.topMaxHeight ?? 0)) -
                          (widget?.topPopConfig?.topMinHeight ?? 0));
                }
              : null,
  
  
  
  複製代碼

• 用Transform包裹抽屜實現根據滑動位移而偏移
  

  class TopPop extends StatelessWidget {
    final double offsetY;
    final double height;
    final double minHeight;
    final double parentHeight;
    final Widget child;
    final Color backgroupColor;
    final bool needDarker;
    final GestureTapCallback onDarkerTap;
  
    TopPop(
        {Key key,
        this.offsetY = 0.0,
        this.height = 0.0,
        this.minHeight = 0.0,
        this.parentHeight = 0.0,
        this.child,
        this.backgroupColor,
        this.needDarker = false,
        this.onDarkerTap})
        : super(key: key);
  
    @override
    Widget build(BuildContext context) {
      double tempOffsetY = 0.0;
      if (offsetY >= 0.0) {
        tempOffsetY = max(0.0, (parentHeight - minHeight));
      } else {
        tempOffsetY = offsetY + max(0.0, (parentHeight - minHeight));
      }
      double opacity = offsetY.abs() / height;
      debugPrint(
          '++++++++offsetY = ${offsetY.toString()}+++++++++opacity = ${opacity.toString()}+++++parentHeight= ${parentHeight.toString()}++ height=${height.toString()}++++++++++minHeight=${minHeight.toString()}+++++++++++++++++++');
      return Stack(
        children: <Widget>[
          needDarker && opacity > 0
              ? GestureDetector(
                  onTap: onDarkerTap,
                  child: Opacity(
                    opacity: opacity,
                    child: Container(
                      width: MediaQuery.of(context).size.width,
                      height: parentHeight,
                      color: Color(0x4C000000),
                    ),
                  ),
                )
              : Container(),
          Transform.translate(
              offset: Offset(0, tempOffsetY),
              child: Container(
                color: backgroupColor ?? Color(0x00000000),
                width: MediaQuery.of(context).size.width,
                height: height,
                child: child,
              ))
        ],
      );
    }
  }
  
  
  
  複製代碼

• 監聽拖動結束事件，並實現自動滑動動畫。
  

  onVerticalDragEnd: (_) {
            if (_offsetY.abs() >
                    (widget?.topPopConfig?.topAutoAnimDistance ?? 20) &&
                topDirection == AxisDirection.up) {
              animateToTop();
            } else {
              animateToBottom();
            }
          },
  
  
  複製代碼

• 監聽拖動開始事件，重置自動滑動動畫
  

  onVerticalDragStart: (_) {
            _animationControllerX?.stop();
            _animationControllerY?.stop();
          },
  
  
  複製代碼

代碼地址：
github.com/sail-coder/…