React Native - Setting TextInput cursor position

问题:

In my React Native app, I am trying to set the cursor position of a TextInput to a particular position (eg. to the 5th character) but am have trouble doing so as the documentation is lacking a little. I suspect it has something to do with the 'setSelection' property of TextInput but I cannot seem to find out what to do.

Has anyone successfully done so?

Thanks.

回答1:

As @this.lau_ says there is a controlled property called selection which accepts an object with keys start and end.

Example:

class ControlledSelectionInput extends Component {
    state = {
        selection: {
            start: 0,
            end: 0
        }
    }

    // selection is an object: { start:number, end:number }
    handleSelectionChange = ({ nativeEvent: { selection } }) => this.setState({ selection })

    render() {
        const { selection } = this.state;

        return <TextInput selection={selection} onSelectionChange={this.handleSelectionChange} />
    }
}

You can also programmatically set the selection by getting a ref to the component and using setNativeProps like this:

this.inputRef.setNativeProps({ selection:{ start:1, end:1 } })

Example:

class SetNativePropsSelectionInput extends Component {
    inputRef = null

    render() {
        const { selection } = this.state;

        return (
            <View>
                <TextInput ref={this.refInput} />
                <Button title="Move selection to start" onPress={this.handleMoveSelectionPress} />
            </View>
    }

    refInput = el => this.inputRef = el

    handleMoveSelectionPress = () => this.input.setNativeProps({
        selection: {
            start: 0,
            end: 0
        }
    })
}

回答2:

There is now a selection property on TextInput which can be used to set the selection or the caret/cursor position.

回答3:

I just know the native way:

public static void adjustCursor(EditText dgInput) {
    CharSequence text = dgInput.getText();
    if (text instanceof Spannable && text.length() > 0) {
        Spannable spanText = (Spannable) text;
        Selection.setSelection(spanText, text.length());
    }
}

Maybe you can find same method in React Native.

回答4:

I don't see any setSelection property in the documentation https://facebook.github.io/react-native/docs/textinput.html, nor do I believe this is supported in core.

If you're doing this in Android, I suggest you take Tiny's code and build your own native component. https://facebook.github.io/react-native/docs/native-modules-android.html#content

Of course, you could do the same in iOS if you have the skills... https://facebook.github.io/react-native/docs/native-modules-ios.html#content

回答5:

It seems like that selection only works when your Text Input is in focus

You can do the following things to make it work

class YourComponent extends React.Component{
      constructor(props) {
       super(props);
       this.state = {
       text:'Hello World',
       selection: {
        start: 0,
        end: 0
       }
  };

this.inputRefs = {};
}

   setSelection = () => {
      this.setState({ select: { start: 1, end: 1 } });
      };

    changeText = (val) => {
     this.inputRefs.input.focus();
    }

    render(){
       return(
          <TextInput 
            onFocus={this.setSelection}
            selection={this.state.setSelection} 
            onChangeText={val => {this.changeText(val)}} 
            value={this.state.text}
             refName={ref => {
             this.inputRefs.input = ref;
             }}
            />
       )
    }
} 

The idea is whenever your TextInput calls the onChangeText call-back put the focus on your TextInput through refs, as your component is responding to onFocus call back we will set the selection on that call back