View React Native:测量视图
我试图使用View React Native:测量视图,view,measure,react-native,View,Measure,React Native,我试图使用ref来测量视图,但是返回的宽度为0,尽管我看到屏幕上显示的视图(它远远不等于0) 我试着这么做:但它就是不起作用。。。我只想得到视图的实际宽度 这是我的密码: var Time = React.createClass({ getInitialState: function() { return({ progressMaxSize: 0 }); }, componentDidMount: function() { this.measureProgressB
ref
来测量视图,但是返回的宽度
为0,尽管我看到屏幕上显示的视图(它远远不等于0)
我试着这么做:但它就是不起作用。。。我只想得到视图的实际宽度
这是我的密码:
var Time = React.createClass({
getInitialState: function() {
return({ progressMaxSize: 0 });
},
componentDidMount: function() {
this.measureProgressBar();
},
measureProgressBar: function() {
this.refs.progressBar.measure(this.setWidthProgressMaxSize);
},
setWidthProgressMaxSize: function(ox, oy, width, height, px, py) {
this.setState({ progressMaxSize: width });
},
render: function() {
return(
<View style={listViewStyle.time} ref="progressBar">
<View style={listViewStyle.progressBar} >
<View style={[listViewStyle.progressMax, { width: this.state.progressMaxSize }]}/>
</View>
</View>
);
}
});
在晚上,一些人谈论了一个(黑客)解决方案,但它解决了我的问题,在这里找到了: 基本上,解决方案是使用
setTimeout
,一切都能神奇地工作:
componentDidMount: function() {
setTimeout(this.measureProgressBar);
},
measureProgressBar: function() {
this.refs.progressBar.measure((a, b, width, height, px, py) =>
this.setState({ progressMaxSize: width })
);
}
您想要测量进度条
var Time=React.createClass({
getInitialState:函数(){
返回({progressMaxSize:0});
},
measureProgressBar:函数(){
this.progressBar.measure(this.setWidthProgressMaxSize);
},
setWidthProgressMaxSize:函数(ox、oy、width、height、px、py){
this.setState({progressMaxSize:width});
},
render:function(){
返回(
{this.progressBar=c;}onLayout={this.measureProgressBar}>
);
}
});
要测量视图大小,根本不需要使用ref。
您可以通过onLayout从nativeEvent获得它
measureView(event: Object) {
console.log(`*** event: ${JSON.stringify(event.nativeEvent)}`);
// you'll get something like this here:
// {"target":1105,"layout":{"y":0,"width":256,"x":32,"height":54.5}}
}
render() {
return (
<View onLayout={(event) => {this.measureView(event)}} />
);
}
measureView(事件:对象){
log(`***事件:${JSON.stringify(event.nativeEvent)}`);
//您将在此处看到类似的内容:
//{“目标”:1105,“布局”:{“y”:0,“宽度”:256,“x”:32,“高度”:54.5}
}
render(){
返回(
{this.measureView(event)}}/>
);
}
您也可以使用requestAnimationFrame。我得到未定义的不是对象(计算'this.refs')
。发生了什么?您需要绑定measureProgressBar,this.measureProgressBar.bind(this)在视图上传递给onLayout
的回调中只调用measure
可能更有效。这是当前最好的解决方案。我使用的是React Native 0.50.4,不推荐使用字符串ref
。此外,View
的measure
功能将不会返回有效数据,除非onLayout
至少触发一次。事实上,有人可以告诉我ox、oy、width、height、px和py的具体含义?onLayout在某些情况下不会特别在Android上调用。这是正确的@umarfaroqawan,但是如果您设置collapsable={false}
,它将始终测量。在Android中,如果没有可见的影响,一些视图将被删除。
var Time = React.createClass({
getInitialState: function() {
return({ progressMaxSize: 0 });
},
measureProgressBar: function() {
this.progressBar.measure(this.setWidthProgressMaxSize);
},
setWidthProgressMaxSize: function(ox, oy, width, height, px, py) {
this.setState({ progressMaxSize: width });
},
render: function() {
return(
<View style={listViewStyle.time} ref={(c) => { this.progressBar = c; } onLayout={this.measureProgressBar}>
<View style={listViewStyle.progressBar} >
<View style={[listViewStyle.progressMax, { width: this.state.progressMaxSize }]}/>
</View>
</View>
);
}
});
measureView(event: Object) {
console.log(`*** event: ${JSON.stringify(event.nativeEvent)}`);
// you'll get something like this here:
// {"target":1105,"layout":{"y":0,"width":256,"x":32,"height":54.5}}
}
render() {
return (
<View onLayout={(event) => {this.measureView(event)}} />
);
}