创建可调整大小的视图，在 FLUTTER 中从角落和侧面捏合或拖动时调整大小

Question

我目前正在开发一个 ScreenView，它具有如上图所示的可拖动和可调整大小的带有角和边的视图等功能。我现在遇到的问题是我想通过角落的触摸手势来调整视图大小。因此，我想到了一个点，我在选择时添加到视图中，可以拖动它来调整所选视图的大小。答案已更新！！

Resizable-Widget ReactNative 演示： React Native PLUGIN example

修改后的可行示例：

  import 'package:flutter/material.dart';

  class ResizeWidget extends StatefulWidget {
    @override
    _ResizeWidgetState createState() => _ResizeWidgetState();
  }

  class _ResizeWidgetState extends State<ResizeWidget> {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        home: Scaffold(
          backgroundColor: Colors.black,
          body: Container(
            // padding: EdgeInsets.only(top: 50),
            child: ResizebleWidget(
              child: Container(
                padding: EdgeInsets.all(10),
                child: Text(
                  'Waao!! you can really dance.',
                  style: TextStyle(
                      color: Colors.white,
                      fontStyle: FontStyle.italic,
                      fontSize: 18),
                ),
              ),
            ),
          ),
        ),
      );
    }
  }

  class ResizebleWidget extends StatefulWidget {
    ResizebleWidget({this.child});

    final Widget child;
    @override
    _ResizebleWidgetState createState() => _ResizebleWidgetState();
  }

  const ballDiameter = 10.0;

  class _ResizebleWidgetState extends State<ResizebleWidget> {
    double height = 100;
    double width = 200;
    bool isCorner = false;

    double top = 0;
    double left = 0;

    @override
    Widget build(BuildContext context) {
      return Stack(
        children: <Widget>[
          Positioned(
            top: top,
            left: left,
            child: Container(
              height: height,
              width: width,

              decoration: BoxDecoration(
                color: Colors.blueGrey,
                border: Border.all(
                  width: 2,
                  color: Colors.white70,
                ),
                borderRadius: BorderRadius.circular(0.0),
              ),

              // need tp check if draggable is done from corner or sides
              child: isCorner
                  ? FittedBox(
                      child: widget.child,
                    )
                  : Center(
                      child: widget.child,
                    ),
            ),
          ),
          // top left
          Positioned(
            top: top - ballDiameter / 2,
            left: left - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var mid = (dx + dy) / 2;
                var newHeight = height - 2 * mid;
                var newWidth = width - 2 * mid;

                setState(() {
                  isCorner = true;
                  height = newHeight > 0 ? newHeight : 0;
                  width = newWidth > 0 ? newWidth : 0;
                  top = top + mid;
                  left = left + mid;
                });
              },
              handlerWidget: HandlerWidget.VERTICAL,
            ),
          ),
          // top middle
          Positioned(
            top: top - ballDiameter / 2,
            left: left + width / 2 - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var newHeight = height - dy;

                setState(() {
                  isCorner = false;

                  height = newHeight > 0 ? newHeight : 0;
                  top = top + dy;
                });
              },
              handlerWidget: HandlerWidget.HORIZONTAL,
            ),
          ),
          // top right
          Positioned(
            top: top - ballDiameter / 2,
            left: left + width - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var mid = (dx + (dy * -1)) / 2;

                var newHeight = height + 2 * mid;
                var newWidth = width + 2 * mid;

                setState(() {
                  isCorner = true;
                  height = newHeight > 0 ? newHeight : 0;
                  width = newWidth > 0 ? newWidth : 0;
                  top = top - mid;
                  left = left - mid;
                });
              },
              handlerWidget: HandlerWidget.VERTICAL,
            ),
          ),
          // center right
          Positioned(
            top: top + height / 2 - ballDiameter / 2,
            left: left + width - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var newWidth = width + dx;

                setState(() {
                  isCorner = false;

                  width = newWidth > 0 ? newWidth : 0;
                });
              },
              handlerWidget: HandlerWidget.HORIZONTAL,
            ),
          ),
          // bottom right
          Positioned(
            top: top + height - ballDiameter / 2,
            left: left + width - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var mid = (dx + dy) / 2;

                var newHeight = height + 2 * mid;
                var newWidth = width + 2 * mid;

                setState(() {
                  isCorner = true;

                  height = newHeight > 0 ? newHeight : 0;
                  width = newWidth > 0 ? newWidth : 0;
                  top = top - mid;
                  left = left - mid;
                });
              },
              handlerWidget: HandlerWidget.VERTICAL,
            ),
          ),
          // bottom center
          Positioned(
            top: top + height - ballDiameter / 2,
            left: left + width / 2 - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var newHeight = height + dy;

                setState(() {
                  isCorner = false;

                  height = newHeight > 0 ? newHeight : 0;
                });
              },
              handlerWidget: HandlerWidget.HORIZONTAL,
            ),
          ),
          // bottom left
          Positioned(
            top: top + height - ballDiameter / 2,
            left: left - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var mid = ((dx * -1) + dy) / 2;

                var newHeight = height + 2 * mid;
                var newWidth = width + 2 * mid;

                setState(() {
                  isCorner = true;

                  height = newHeight > 0 ? newHeight : 0;
                  width = newWidth > 0 ? newWidth : 0;
                  top = top - mid;
                  left = left - mid;
                });
              },
              handlerWidget: HandlerWidget.VERTICAL,
            ),
          ),
          //left center
          Positioned(
            top: top + height / 2 - ballDiameter / 2,
            left: left - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                var newWidth = width - dx;

                setState(() {
                  isCorner = false;

                  width = newWidth > 0 ? newWidth : 0;
                  left = left + dx;
                });
              },
              handlerWidget: HandlerWidget.HORIZONTAL,
            ),
          ),
          // center center
          Positioned(
            top: top + height / 2 - ballDiameter / 2,
            left: left + width / 2 - ballDiameter / 2,
            child: ManipulatingBall(
              onDrag: (dx, dy) {
                setState(() {
                  isCorner = false;

                  top = top + dy;
                  left = left + dx;
                });
              },
              handlerWidget: HandlerWidget.VERTICAL,
            ),
          ),
        ],
      );
    }
  }

  class ManipulatingBall extends StatefulWidget {
    ManipulatingBall({Key key, this.onDrag, this.handlerWidget});

    final Function onDrag;
    final HandlerWidget handlerWidget;

    @override
    _ManipulatingBallState createState() => _ManipulatingBallState();
  }

  enum HandlerWidget { HORIZONTAL, VERTICAL }

  class _ManipulatingBallState extends State<ManipulatingBall> {
    double initX;
    double initY;

    _handleDrag(details) {
      setState(() {
        initX = details.globalPosition.dx;
        initY = details.globalPosition.dy;
      });
    }

    _handleUpdate(details) {
      var dx = details.globalPosition.dx - initX;
      var dy = details.globalPosition.dy - initY;
      initX = details.globalPosition.dx;
      initY = details.globalPosition.dy;
      widget.onDrag(dx, dy);
    }

    @override
    Widget build(BuildContext context) {
      return GestureDetector(
        onPanStart: _handleDrag,
        onPanUpdate: _handleUpdate,
        child: Container(
          width: ballDiameter,
          height: ballDiameter,
          decoration: BoxDecoration(
            color: Colors.white,
            shape: this.widget.handlerWidget == HandlerWidget.VERTICAL
                ? BoxShape.circle
                : BoxShape.rectangle,
          ),
        ),
      );
    }
  }

输出：

Answer 1

已更新

我做了一个简单的原型来展示这个想法。

绘制大小处理程序和容器；
使用 GestureDetector 检测拖动；
刷新主容器大小和坐标。

    import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Text Overflow Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Demo(),
      ),
    );
  }
}

class Demo extends StatefulWidget {
  @override
  _DemoState createState() => _DemoState();
}

class _DemoState extends State<Demo> {
  @override
  Widget build(BuildContext context) {
    return Container(
      padding: EdgeInsets.all(60),
      child: ResizebleWidget(
        child: Text(
'''I've just did simple prototype to show main idea.
  1. Draw size handlers with container;
  2. Use GestureDetector to get new variables of sizes
  3. Refresh the main container size.''',
        ),
      ),
    );
  }
}

class ResizebleWidget extends StatefulWidget {
  ResizebleWidget({this.child});

  final Widget child;
  @override
  _ResizebleWidgetState createState() => _ResizebleWidgetState();
}

const ballDiameter = 30.0;

class _ResizebleWidgetState extends State<ResizebleWidget> {
  double height = 400;
  double width = 200;

  double top = 0;
  double left = 0;

  void onDrag(double dx, double dy) {
    var newHeight = height + dy;
    var newWidth = width + dx;

    setState(() {
      height = newHeight > 0 ? newHeight : 0;
      width = newWidth > 0 ? newWidth : 0;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Positioned(
          top: top,
          left: left,
          child: Container(
            height: height,
            width: width,
            color: Colors.red[100],
            child: widget.child,
          ),
        ),
        // top left
        Positioned(
          top: top - ballDiameter / 2,
          left: left - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var mid = (dx + dy) / 2;
              var newHeight = height - 2 * mid;
              var newWidth = width - 2 * mid;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
                width = newWidth > 0 ? newWidth : 0;
                top = top + mid;
                left = left + mid;
              });
            },
          ),
        ),
        // top middle
        Positioned(
          top: top - ballDiameter / 2,
          left: left + width / 2 - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var newHeight = height - dy;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
                top = top + dy;
              });
            },
          ),
        ),
        // top right
        Positioned(
          top: top - ballDiameter / 2,
          left: left + width - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var mid = (dx + (dy * -1)) / 2;

              var newHeight = height + 2 * mid;
              var newWidth = width + 2 * mid;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
                width = newWidth > 0 ? newWidth : 0;
                top = top - mid;
                left = left - mid;
              });
            },
          ),
        ),
        // center right
        Positioned(
          top: top + height / 2 - ballDiameter / 2,
          left: left + width - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var newWidth = width + dx;

              setState(() {
                width = newWidth > 0 ? newWidth : 0;
              });
            },
          ),
        ),
        // bottom right
        Positioned(
          top: top + height - ballDiameter / 2,
          left: left + width - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var mid = (dx + dy) / 2;

              var newHeight = height + 2 * mid;
              var newWidth = width + 2 * mid;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
                width = newWidth > 0 ? newWidth : 0;
                top = top - mid;
                left = left - mid;
              });
            },
          ),
        ),
        // bottom center
        Positioned(
          top: top + height - ballDiameter / 2,
          left: left + width / 2 - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var newHeight = height + dy;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
              });
            },
          ),
        ),
        // bottom left
        Positioned(
          top: top + height - ballDiameter / 2,
          left: left - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var mid = ((dx * -1) + dy) / 2;

              var newHeight = height + 2 * mid;
              var newWidth = width + 2 * mid;

              setState(() {
                height = newHeight > 0 ? newHeight : 0;
                width = newWidth > 0 ? newWidth : 0;
                top = top - mid;
                left = left - mid;
              });
            },
          ),
        ),
        //left center
        Positioned(
          top: top + height / 2 - ballDiameter / 2,
          left: left - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              var newWidth = width - dx;

              setState(() {
                width = newWidth > 0 ? newWidth : 0;
                left = left + dx;
              });
            },
          ),
        ),
        // center center
        Positioned(
          top: top + height / 2 - ballDiameter / 2,
          left: left + width / 2 - ballDiameter / 2,
          child: ManipulatingBall(
            onDrag: (dx, dy) {
              setState(() {
                top = top + dy;
                left = left + dx;
              });
            },
          ),
        ),
      ],
    );
  }
}

class ManipulatingBall extends StatefulWidget {
  ManipulatingBall({Key key, this.onDrag});

  final Function onDrag;

  @override
  _ManipulatingBallState createState() => _ManipulatingBallState();
}

class _ManipulatingBallState extends State<ManipulatingBall> {
  double initX;
  double initY;

  _handleDrag(details) {
    setState(() {
      initX = details.globalPosition.dx;
      initY = details.globalPosition.dy;
    });
  }

  _handleUpdate(details) {
    var dx = details.globalPosition.dx - initX;
    var dy = details.globalPosition.dy - initY;
    initX = details.globalPosition.dx;
    initY = details.globalPosition.dy;
    widget.onDrag(dx, dy);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanStart: _handleDrag,
      onPanUpdate: _handleUpdate,
      child: Container(
        width: ballDiameter,
        height: ballDiameter,
        decoration: BoxDecoration(
          color: Colors.blue.withOpacity(0.5),
          shape: BoxShape.circle,
        ),
      ),
    );
  }
}

Answer 2

如果上面的代码对任何人有帮助，我做了一个离散版本（即每 50 个单元捕捉一次）：

    import 'package:flutter/material.dart';
    
    class DiscreteResizableComponent extends StatefulWidget {
      const DiscreteResizableComponent({Key key, this.child}):super(key:key);
    
      final Widget child;
      @override
      _ResizebleWidgetState createState() => _ResizebleWidgetState();
    }
    
    const ballDiameter = 30.0;
    const discreteStepSize = 50;
    
    class _ResizebleWidgetState extends State<DiscreteResizableComponent> {
      double height = 400;
      double width = 200;
    
      double top = 0;
      double left = 0;
    
      double cumulativeDy=0;
      double cumulativeDx=0;
      double cumulativeMid = 0;
    
      void onDrag(double dx, double dy) {
        var newHeight = height + dy;
        var newWidth = width + dx;
    
        setState(() {
          height = newHeight > 0 ? newHeight : 0;
          width = newWidth > 0 ? newWidth : 0;
        });
      }
    
      @override
      Widget build(BuildContext context) {
        return Stack(
          children: <Widget>[
            Positioned(
              top: top,
              left: left,
              child: Container(
                height: height,
                width: width,
                color: Colors.red[100],
                child: widget.child,
              ),
            ),
            // top left
            Positioned(
              top: top - ballDiameter / 2,
              left: left - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  var mid = (dx + dy) / 2;
                  cumulativeMid -= 2*mid;
                  if(cumulativeMid>=discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height+discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width +discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                  else if(cumulativeMid<=-discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height - discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width - discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                },
              ),
            ),
            // top middle
            Positioned(
              top: top - ballDiameter / 2,
              left: left + width / 2 - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  cumulativeDy -= dy;
                  if(cumulativeDy>=discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height+discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      cumulativeDy=0;
                    });
                  }
                  else if(cumulativeDy<=-discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height - discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      cumulativeDy=0;
                    });
                  }
                },
              ),
            ),
            // top right
            Positioned(
              top: top - ballDiameter / 2,
              left: left + width - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  var mid = (dx + (dy * -1)) / 2;
                  cumulativeMid += 2*mid;
                  if(cumulativeMid>=discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height+discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width +discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                  else if(cumulativeMid<=-discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height - discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width - discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                },
              ),
            ),
            // center right
            Positioned(
              top: top + height / 2 - ballDiameter / 2,
              left: left + width - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  cumulativeDx += dx;
    
                  if(cumulativeDx>=discreteStepSize)
                  {
                    setState(() {
                      var newWidth = width+discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeDx=0;
                    });
                  }
                  else if(cumulativeDx<=-discreteStepSize)
                  {
                    setState(() {
                      var newWidth = width-discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeDx=0;
                    });
                  }
                },
              ),
            ),
            // bottom right
            Positioned(
              top: top + height - ballDiameter / 2,
              left: left + width - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  var mid = (dx + dy) / 2;
    
                  cumulativeMid += 2*mid;
                  if(cumulativeMid>=discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height+discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width +discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                  else if(cumulativeMid<=-discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height - discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width - discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                },
              ),
            ),
            // bottom center
            Positioned(
              top: top + height - ballDiameter / 2,
              left: left + width / 2 - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  cumulativeDy += dy;
    
                  if(cumulativeDy>=discreteStepSize)
                    {
                      setState(() {
                        var newHeight = height+discreteStepSize;
                        height = newHeight > 0 ? newHeight : 0;
                        cumulativeDy=0;
                      });
                    }
                  else if(cumulativeDy<=-discreteStepSize)
                    {
                      setState(() {
                        var newHeight = height-discreteStepSize;
                        height = newHeight > 0 ? newHeight : 0;
                        cumulativeDy=0;
                      });
                    }
                },
              ),
            ),
            // bottom left
            Positioned(
              top: top + height - ballDiameter / 2,
              left: left - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  var mid = ((dx * -1) + dy) / 2;
    
                  cumulativeMid += 2*mid;
                  if(cumulativeMid>=discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height+discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width +discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                  else if(cumulativeMid<=-discreteStepSize)
                  {
                    setState(() {
                      var newHeight = height - discreteStepSize;
                      height = newHeight > 0 ? newHeight : 0;
                      var newWidth = width - discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeMid=0;
                    });
                  }
                },
              ),
            ),
            //left center
            Positioned(
              top: top + height / 2 - ballDiameter / 2,
              left: left - ballDiameter / 2,
              child: ManipulatingBall(
                onDrag: (dx, dy) {
                  cumulativeDx -= dx;
    
                  if(cumulativeDx>=discreteStepSize)
                  {
                    setState(() {
                      var newWidth = width+discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeDx=0;
                    });
                  }
                  else if(cumulativeDx<=-discreteStepSize)
                  {
                    setState(() {
                      var newWidth = width-discreteStepSize;
                      width = newWidth > 0 ? newWidth : 0;
                      cumulativeDx=0;
                    });
                  }
                },
              ),
            ),
          ],
        );
      }
    }
    
    class ManipulatingBall extends StatefulWidget {
      ManipulatingBall({Key key, this.onDrag});
    
      final Function onDrag;
    
      @override
      _ManipulatingBallState createState() => _ManipulatingBallState();
    }
    
    class _ManipulatingBallState extends State<ManipulatingBall> {
      double initX;
      double initY;
    
      _handleDrag(details) {
        setState(() {
          initX = details.globalPosition.dx;
          initY = details.globalPosition.dy;
        });
      }
    
      _handleUpdate(details) {
        var dx = details.globalPosition.dx - initX;
        var dy = details.globalPosition.dy - initY;
        initX = details.globalPosition.dx;
        initY = details.globalPosition.dy;
        widget.onDrag(dx, dy);
      }
    
      @override
      Widget build(BuildContext context) {
        return GestureDetector(
          onPanStart: _handleDrag,
          onPanUpdate: _handleUpdate,
          child: Container(
            width: ballDiameter,
            height: ballDiameter,
            decoration: BoxDecoration(
              color: Colors.blue.withOpacity(0.5),
              shape: BoxShape.circle,
            ),
          ),
        );
      }
    }

创建可调整大小的视图，在 FLUTTER 中从角落和侧面捏合或拖动时调整大小

Creating Resizable View that resizes when pinch or drag from corners and sides in FLUTTER

resize

image-resizing

window-resize

flutter

flutter-layout