How to get the current number of lines in String of TextInput?

Question

After entering text in TextInput I want to know the currunt number of lines in TextInput. Or The current number of strings is also pos

Answer 1

As far as I know, there is no offical way to get the currently used number of lines, but I have a workaround for you:

We make use of the onLayout method of our TextInput and we keep track of the currently used height. We need two state variables:

this.state = {
      height: 0, // here we track the currently used height
      usedLines: 0,// here we calculate the currently used lines 
    }

onLayout:

  _onLayout(e) {
     console.log('e', e.nativeEvent.layout.height);
     // the height increased therefore we also increase the usedLine counter
     if (this.state.height < e.nativeEvent.layout.height) {
         this.setState({usedLines: this.state.usedLines+1}); 
     } 
     // the height decreased, we subtract a line from the line counter 
     if (this.state.height > e.nativeEvent.layout.height){
         this.setState({usedLines: this.state.usedLines-1}); 
     }
     // update height if necessary
     if (this.state.height != e.nativeEvent.layout.height){
         this.setState({height: e.nativeEvent.layout.height});
     }

  }

Render Method

  render() {
    console.log('usedLines', this.state.usedLines);
    return (
      
         this._onLayout(e)} />
      
    );
  }

Working Example:

https://snack.expo.io/B1vC8dvJH