概述

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OneSequenceGestureRecognizer.addAllowedPointer() 已更改为接受 PointerDownEvent,就像其超类一样。之前,它接受更通用的 PointerEvent 类型,这是不正确的。

背景

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框架仅将 PointerDownEvent 对象传递给 addAllowedPointer()。将 OneSequenceGestureRecognizer.addAllowedPointer() 声明为接受更通用的类型会造成混淆,并导致 OneSequenceGestureRecognizer 的子类必须将其参数转换为正确的类。

变更说明

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先前的声明强制 OneSequenceGestureRecognizer 的后代像这样覆盖 addAllowedPointer()

dart
class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

新的方法声明将导致此代码因以下错误消息而失败

super.addAllowedPointer(event); The argument type 'PointerEvent' can't be assigned to the parameter type 'PointerDownEvent'.
                                #argument_type_not_assignable

迁移指南

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迁移前的代码

dart
class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

迁移后的代码

dart
class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerDownEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

时间线

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发布于版本:2.3.0-13.0.pre
稳定版本:2.5

参考资料

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API 文档

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