add one to textinput value on button press in react-native

Question

I have this button and input

 <Button style={styles.button, {overflow: 'hidden' }} onPress={this.ADDONE}>   ADD </Button>
 <TextInput ref={component => this._textInput = component}
 style={{height: 40, borderColor: 'gray',width:120}
           value={this.state.text}  defaultValue='N.m' />

and here is my try

ADDONE:function(){      
   var va=this.state._textInput;      
   if(va == "" || va == "undefined"){va=0}    
   va=va+1;
    this._textInput.setNativeProps({text: va});    
},

what I need is when I press on button to add 1 to input value every time the button event is "onpress=function"

Now it can't increase 1 because it is string not number I tried this

var va=this.state._textInput;
  var  nn= {properties: { value: 0 }};
   if(va == 'N.m' || va == undefined){va=0;}
nn=va;
   nn=nn+1;
 va = nn ;
    this._textInput.setNativeProps({text: va});

it just give a right behvaior at the first time only after that it can't parse text to int please help

Answer 1

Maybe you're trying to do something I'm not quite understanding, but this seems over-engineered to me. If all you need is to add +1 to a variable when a button is pressed, then try this...

constructor(props){
   this.super(props);
   this.state = {
      va = 0,
   }
}

render(){
  <Button
    onPress={() => this.setState({va: this.state.va++})} >
    ADD
  </Button>
}

And by the way, I'm pretty sure you need to update your style declaration by wrapping it in an array like so...

style={[styles.button, {overflow: 'hidden' }]}