Javascript null不是对象(计算';this.state.token';)反应本机
我试图在视图中运行类,但出现以下错误: null不是对象(正在计算“this.state.token”) 这是我尝试渲染的类:Javascript null不是对象(计算';this.state.token';)反应本机,javascript,reactjs,react-native,Javascript,Reactjs,React Native,我试图在视图中运行类,但出现以下错误: null不是对象(正在计算“this.state.token”) 这是我尝试渲染的类: class BackEnd extends Component{ render() { if (this.state.token) { return ( <ListView dataSource={this.state.users} renderRow={this.renderUsers} sty
class BackEnd extends Component{
render() {
if (this.state.token) {
return (
<ListView dataSource={this.state.users}
renderRow={this.renderUsers}
style={styles.listView} />
);
} else {
return (
<View style={styles.container}>
<Text style={styles.welcome}>
Mobil
</Text>
<TextInput
style={styles.textInput}
onChangeText={(username) => this.setState({'username': username})}
value= {this.state.username}
/>
<TextInput
secureTextEntry={true}
style={styles.textInput}
onChangeText={(password) => this.setState({'password': password})}
value={this.state.password}
/>
<TouchableHighlight style={styles.button} onPress={ () => this.getToken(config.client_id, config.client_key, this.state.username, this.state.password)}>
<Text>Login</Text>
</TouchableHighlight>
<Text style={styles.error}>
{this.state.error}
</Text>
</View>
)};
}
}
我在render函数中这样调用后端类:
case 'item2':
content =
<View>
<BackEnd/>
<Text style={styles.instructions}> Hier komt het
(school)rooster</Text>
</View>
break
案例“item2”:
内容=
海尔科姆特酒店
(学校)公鸡
打破
堆栈跟踪:
null不是对象(正在计算“this.state.token”)
提供
C:\Users\Mansur\Documents\AwesomeProject\src\Smartplanner.js:64:21
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:1045:14
测量误差
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:85:11
_RenderValidatedComponent没有自己的或上下文
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:1045:8
_renderValidatedComponent
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\react compositecomponent.js:1075:10
性能计数
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:484:24
挂载组件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:346:40
挂载组件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\ReactReconciler.js:62:6
更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\react childreconciler.js:157:10
_和解更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:212:10
_更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:345:6
更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:331:25
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\native\ReactNativeBaseComponent.js:130:24
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\ReactReconciler.js:163:38
_updateRenderedComponent
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:982:8
_performComponentUpdate
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:944:34
更新组件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:847:8
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\react compositecomponent.js:710:6
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\ReactReconciler.js:163:38
更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\react childreconciler.js:143:10
_和解更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:212:10
_更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:345:6
更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\shared\stack\reconciler\ReactMultiChild.js:331:25
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renderers\native\ReactNativeBaseComponent.js:130:24
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\ReactReconciler.js:163:38
_updateRenderedComponent
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:982:8
_performComponentUpdate
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:944:34
更新组件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\ReactCompositeComponent.js:847:8
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\renders\src\renders\shared\stack\reconciler\react compositecomponent.js:710:6
接收元件
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\ReactReconciler.js:163:38
更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libraries\Renderer\src\renders\shared\stack\reconciler\react childreconciler.js:143:10
_和解更新儿童
C:\Users\Mansur\Documents\AwesomeProject\node\u modules\react native\Libra
case 'item2':
content =
<View>
<BackEnd/>
<Text style={styles.instructions}> Hier komt het
(school)rooster</Text>
</View>
break