我遇到一个非常简单的问题.我有用户名,密码和按钮的登录表单.在我的按钮处理程序中,我尝试获取textinput值.但总是得到未定义的价值.我错过了什么吗？
render() {
<ExScreen
headerColor={this.state.headerColor}
scrollEnabled={this.state.enableScroll}
style={styles.container} >
<View >
<View >
<View style={[styles.inputContainer]} >
<TextInput
ref= "username"
onChangeText={(text) => this.setState({text})}
value={this.state.username}
/>
</View>
<Button style={{color: 'white',marginTop: 30,borderWidth: 1,borderColor: 'white',marginLeft: 20*vw,marginRight: 20*vw,height: 40,padding: 10}}
onPress={this._handlePress.bind(this)}>
Sign In
</Button>
...
_handlePress(event) {
var username=this.refs.username.value;
