ReactNative: TextInput disappear in FlexLayout

Question

I'm learning react-native,when I trying to use TextInput component in a flex layout, it disappear .

index.android.js

//....
render(){
    return (
        <View style={  {flex:1,flexDirection:'row'}}>
            <TextInput placeholder="test"/>
        </View>
    )
}

//....

I was very confused.

Answer 1

I tried to set TextInput's height , but it doesn't work. And I finally success to set width or {flex:1} to TextInput. I think, when the parant container been set {flexDirection:"row"}, TextInput's width is 0, so I can't see it. By default,the parent container's flex direction is 'column',TextInput Element adjust itself's {flex:1} to fill the parent container.