title: Creating a Number Changer with TextInput in React Native
body: <p>I'm trying create a Number Incrementor/Decrementor with the use of Text Input and 2 Touch Highlights "+" and "-".</p>
  
  <pre><code>&lt;TextInput
    keyboardType='number-pad'
    value={this.state.textValue}
    onChangeText={this.updateText}
    style={styles.textInput}
  /&gt;
  
  &lt;TouchableHighlight
    style={styles.button}
    onPress={this.increment}&gt;
      &lt;Text style={styles.buttonTextFill}&gt;+&lt;/Text&gt;
  &lt;/TouchableHighlight&gt;
  
  &lt;TouchableHighlight
    style={styles.button}
    onPress={this.decrement}&gt;
      &lt;Text style={styles.buttonTextFill}&gt;-&lt;/Text&gt;
  &lt;/TouchableHighlight&gt;
  </code></pre>
  
  <p>And I use the following methods:</p>
  
  <pre><code>updateText: function (text) {
      this.setState({textValue: text});
  },
  
  decrement: function () {
      this.setState({textValue: this.state.textValue - 1});
  },
  
  increment: function () {
      this.setState({textValue: this.state.textValue + 1});
  },
  </code></pre>
  
  <p>Also I have set <strong>textValue</strong> as a state in getInitialState function and set it to 0.</p>
  
  <p>Why isn't this working, what am I doing wrong?</p>