[英]undefined is not object React Native
我越來越清楚,當嘗試從navigationOptions的上下文調用this.refs時,未定義的錯誤不是對象。
如果我用代碼解釋更好:
static navigationOptions = ({ navigation, screenProps }) => ({
headerTitle: 'my app',
title: 'my app',
headerTitleStyle: {
textAlign: "center",
flex: 1,
},
headerLeft:
<TouchableOpacity style={{padding: 15, marginLeft: 5}} onPress={() => { navigation.state.params.goBack(navigation.state.params.canGoBack) }}>
{navigation.state.params.canGoBack ? <Text>back</Text>: <Text>close</Text>}
</TouchableOpacity>,
});
componentDidMount() {
this.props.navigation.setParams({goBack: this.onBack});
this.props.navigation.setParams({canGoBack: this.state.canGoBack});
Keyboard.dismiss();
}
onBack(canGoBack) {
console.log(canGoBack);
if(canGoBack){
this.refs[WEBVIEW_REF].goBack(); // here is the error happening, somehow I can access this.refs.
}
}
onNavigationStateChange(navState) {
this.setState({
canGoBack: navState.canGoBack
});
this.props.navigation.setParams({
canGoBack: this.state.canGoBack,
});
console.log("some action happened: " + this.state.canGoBack);
}
有人知道如何解決嗎?
問題是您在使用this.onBack
時會丟失上下文
您需要確保在組件上下文中調用this.onBack
,並且可以通過以下兩種方法之一進行操作:
使用arrow functions
: this.props.navigation.setParams({goBack: (e) => this.onBack(e)});
this
綁定到您的函數: this.props.navigation.setParams({goBack: this.onBack.bind(this)});
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