title: How do I overlay ActivityIndicator in react-native?
body: <p>I have a View with few form elements and a button (TouchableHighlight). On clicking the button, an Activity Indicator should be shown as an overlay to the existing view. The Activity Indicator should be centered within the page and the existing view should be slightly blurred to indicate overlay. I tried different options but could not get it to work.</p>
  
  <pre><code>render() {
      const { username, password } = this.state;
  
      return (
          &lt;View style={styles.container}&gt;
              &lt;View style={styles.group}&gt;
                  &lt;Text style={styles.text}&gt;Username:&lt;/Text&gt;
                  &lt;TextInput
                      style={styles.input}
                      onChangeText={this.handleUserNameChange.bind(this)}
                      value={username}
                      underlineColorAndroid="transparent"
                  /&gt;
              &lt;/View&gt;
              &lt;View style={styles.group}&gt;
                  &lt;Text style={styles.text}&gt;Password:&lt;/Text&gt;
                  &lt;TextInput
                      style={styles.input}
                      secureTextEntry={true}
                      onChangeText={this.handlePasswordChange.bind(this)}
                      value={password}
                      underlineColorAndroid="transparent"
                  /&gt;
              &lt;/View&gt;
              &lt;TouchableHighlight
                  style={styles.button}
                  onPress={this.handleLogin.bind(this)}&gt;
                  &lt;Text style={styles.buttonText}&gt;Logon&lt;/Text&gt;
              &lt;/TouchableHighlight&gt;
          &lt;/View&gt;
      );
  }
  </code></pre>
  
  <p>Existing styles:</p>
  
  <pre><code>const styles = StyleSheet.create({
      container: {
          flex: 1,
          justifyContent: 'flex-start',
          alignItems: 'center',
          backgroundColor: '#F5FCFF',
          marginTop: 60
      },
      group: {
          alignItems: 'flex-start',
          padding: 10
      },
      input: {
          width: 150,
          padding: 2,
          paddingLeft: 5,
          borderColor: 'gray',
          borderWidth: 1
      },
      text: {
          padding: 0
      },
      button: {
          width: 150,
          backgroundColor: '#2299F2',
          padding: 15,
          marginTop: 20,
          borderRadius: 5
      },
      buttonText: {
          textAlign: 'center',
          color: '#fff',
          fontSize: 24
      },
  });
  </code></pre>
  
  <p>I need to an ActivityIndicator to the above View, overlay the view, and center the ActivityIndicator.</p>