LinearProgressIndicator

LinearProgressIndicator

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LinearProgressIndicator颤动用法

本文介绍了LinearProgressIndicator颤动用法的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在学习Flutter的所有想法，我不知道它是否正确.我想以任何方式使用Material Librery的LinearProgressIndicator组件，但我没有得到使用方法，我尝试了以下代码:

I am learning Flutter allthought i dont know if it is right decition or not. Any way i want to use LinearProgressIndicator Component from Material Librery but i didnt get how to use it i tried this code:

import 'dart:async';
import 'package:flutter/material.dart';

void main() {
runApp(new MaterialApp(
debugShowCheckedModeBanner: false,
home: new MyApp(),
 ));
}

class MyApp extends StatefulWidget {
@override
MyAppState createState() => new MyAppState();
}

class MyAppState extends State<MyApp> {
@override
Widget build(BuildContext context) {
return new Scaffold(
  appBar: new AppBar(
    title: new Text('Slider Demo'),
  ),
  body: new Container(
    color: Colors.blueAccent,
    padding: new EdgeInsets.all(32.0),
    child: new ProgressIndicatorDemo(),
  ),
);
}
}

class ProgressIndicatorDemo extends StatefulWidget {

@override
_ProgressIndicatorDemoState createState() =>
  new _ProgressIndicatorDemoState();
}

class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo>
with SingleTickerProviderStateMixin {
AnimationController _controller;

@override
void initState() {
super.initState();
_controller = new AnimationController(
  duration: const Duration(milliseconds: 1500),
  vsync: this,
);
_playAnimation();
}

 Future<Null> _playAnimation() async {
  try {
  await _controller.repeat().orCancel;
  } on TickerCanceled {
  // the animation got canceled, probably because we were disposed
  }
  }

  @override
  void dispose() {
  _controller.stop();
  super.dispose();
  }

  @override
  Widget build(BuildContext context) {
  return _buildAnimation(context, null);
 }

 Widget _buildAnimation(BuildContext context, Widget child) {
 return new Center(
    child: new Container(
  color: Colors.redAccent.withOpacity(.1),
  child: new LinearProgressIndicator(
    value: _controller.value,
    backgroundColor: Colors.redAccent,
  ),
   ));
  }
 }

但我总是收到此错误

I/flutter ( 3819): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY 
╞═══════════════════════════════════════════════════════════
I/flutter ( 3819): The following NoSuchMethodError was thrown building 
ProgressIndicatorDemo(dirty, state:
I/flutter ( 3819): _ProgressIndicatorDemoState#80400(ticker active)):
I/flutter ( 3819): The getter 'value' was called on null.
I/flutter ( 3819): Receiver: null
I/flutter ( 3819): Tried calling: value
I/flutter ( 3819):
I/flutter ( 3819): When the exception was thrown, this was the stack:
I/flutter ( 3819): #0      Object.noSuchMethod 
(dart:core/runtime/libobject_patch.dart:46:5)
I/flutter ( 3819): #1      _ProgressIndicatorDemoState.build 
(file:///E:/Flutter_work/animation_test/lib/main.dart:67:26)
I/flutter ( 3819): #2      StatefulElement.build 
(package:flutter/src/widgets/framework.dart:3730:27)
I/flutter ( 3819): #3      ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3642:15)
I/flutter ( 3819): #4      Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #5      StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #6      Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #7      SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 3819): #8      Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #9      SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 3819): #10     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #11     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #12     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #13     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 3819): #14     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #15     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #16     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #17     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 3819): #18     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #19     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #20     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #21     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 3819): #22     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #23     RenderObjectElement.updateChildren 
(package:flutter/src/widgets/framework.dart:4379:32)
I/flutter ( 3819): #24     MultiChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4769:17)
I/flutter ( 3819): #25     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #26     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #27     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #28     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #29     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #30     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #31     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #32     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 3819): #33     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #34     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #35     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #36     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #37     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #38     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 3819): #39     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #40     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #41     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #42     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 3819): #43     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)   
I/flutter ( 3819): #44     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 3819): #45     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #46     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #47     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #48     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #49     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #50     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #51     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #52     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #53     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #54     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #55     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #56     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 3819): #57     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #58     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #59     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #60     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 3819): #61     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #62     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #63     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 3819): #64     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 3819): #65     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 3819): #66     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 3819): #67     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3495:5)  
I/flutter ( 3819): #68     BuildOwner.buildScope 
(package:flutter/src/widgets/framework.dart:2242:33)
 Reloaded 0 of 391 libraries in 829ms.
 Lost connection to device.

如何解决这个问题，我很想做这个演示 Flutter进度指示器演示，但结果也是一样的任何人都可以在我的示例中帮助我，或者可以告诉我代码中的错误是什么?问候

How to slove that and i treid to do this Demo Flutter Progress Indicator Demo but Also the same Result Any one can help me in working example about that or can tell me what is the wrong in my code ??Regards

推荐答案

您没有使用动画对象.

import 'dart:async';
import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    debugShowCheckedModeBanner: false,
    home: new MyApp(),
  ));
}

class MyApp extends StatefulWidget {
  @override
  MyAppState createState() => new MyAppState();
}

class MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Slider Demo'),
      ),
      body: new Container(
        color: Colors.blueAccent,
        padding: new EdgeInsets.all(32.0),
        child: new ProgressIndicatorDemo(),
      ),
    );
  }
}

class ProgressIndicatorDemo extends StatefulWidget {

  @override
  _ProgressIndicatorDemoState createState() =>
      new _ProgressIndicatorDemoState();
}

class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo>
    with SingleTickerProviderStateMixin {
  AnimationController controller;
  Animation<double> animation;

  @override
  void initState() {
    super.initState();
    controller = AnimationController(
        duration: const Duration(milliseconds: 2000), vsync: this);
    animation = Tween(begin: 0.0, end: 1.0).animate(controller)
      ..addListener(() {
        setState(() {
          // the state that has changed here is the animation object’s value
        });
      });
    controller.repeat();
  }


  @override
  void dispose() {
    controller.stop();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Center(
        child: new Container(
          child:  LinearProgressIndicator( value:  animation.value,),

        )
    );
  }

}

这篇关于LinearProgressIndicator颤动用法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

09-17 12:12
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