Question

现在我有一个学校项目在手机上构建应用程序。我们正在使用React Native和Java。我想在应用程序中创建一个按钮，当按下该按钮时会变为随机颜色。但是，这不起作用。

以下是我的代码片段：

    export default class HomeScreen extends React.Component {

  constructor(props) {
  super(props);
  this.state = {color: "#000000"}
}
  render() {

    let color = this.state.color;
  return (

...

<View>
          <Button
          onPress = {changecolor}
          title = "This button changes color when pressed"
          color = {color}/>
        </View>

...

numbers = ["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"];

this.random = this.numbers[Math.floor(Math.random() * this.numbers.length)];

function changecolor() {
  this.replaceState({color: String("#"+random+random+random+random+random+random)});
}

在按钮仅变成灰色阴影而不是任何颜色之前，我还有一个问题。有什么帮助吗？

编辑：我应该提到我以前使用过this.setState，并且结果相同

Answer 1

  export default class HomeScreen extends React.Component {

    constructor(props) {
        super(props);
        this.state = {color: "#000000"}
    }

    render() {

    let color = this.state.color;
    return (
    <View>
        <Button
        onPress = {this.changecolor}
        title = "This button changes color when pressed"
        color = {color}/>
    </View>


    numbers = ["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"];

    this.random = this.numbers[Math.floor(Math.random() * this.numbers.length)];

    changecolor() {
        this.replaceState({color: String("#"+random+random+random+random+random+random)});
    }
}

Answer 2

changecolor甚至是HomeScreen类的成员吗？看起来好像不是这样，考虑到它是用function声明的，并且没有解析错误在向您尖叫。使其成为一种方法，更好的是，使它成为箭头函数：

changecolor = () => {
  this.replaceState({color: String("#"+random+random+random+random+random+random)});
}

我不断收到一条错误消息，说this.replaceState不是一个函数

2 个答案: