Question

TypeError：未定义不是一个对象（评估“route.params.myText”）

2022-01-23

492

javascript reactjs react-native

function Screen2({route, navigation}) {
  
    
    return (
      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
        <Text>{route.params.myText}</Text>
      </View>
    );
  }

export default Screen2;

这里的 myText 是从其他屏幕（登录屏幕）传递过来的字符串。

登录屏幕---------------------------------------

<View>
                <Button style={styles.loginBTN} title="Login"
                onPress={() => {navigation.navigate('Screen2'), {myText: "hello react-native"}}} />
            </View>

Answer 1

我猜有一种情况（可能在卸载之前）是 route 或 route.params 未定义，

你可以用这种方法解决

function Screen2({route, navigation}) {  
    return (
      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>

        //I added question mark before the dots (optional chaining)
        <Text>{route?.params?.myText}</Text>
      </View>
    );
  }
export default Screen2;

它被称为可选链接，根据 Mozilla

It enables you to read the value of a property located deep within a chain of connected objects without having to check that each reference in the chain is valid.

Answer 2

您按下登录按钮应传递如下参数

onPress={() = navigation.navigate("Screen2", {
          myText: "hello react-native",
        })
}