Question

异步等待不起作用。我需要等待图像加载，进入一个状态然后继续前进。不起作用。

export default () => {
  const [imgTmp, setImgTmp] = useState(null);

  const chooseImage = async () => {
    await ImagePicker.showImagePicker('', r => {
      if (r.uri) {
        let img = {uri: r.uri};
        setImgTmp(img);
      }
    });
    alert('...');
  };

  return (
    <View>
      <View style={{height: 40, backgroundColor: '#DDDD'}}>
        <Image source={imgTmp} style={{width: 100, height: 100}} />
      </View>
      <Button title="Select Imagem" onPress={chooseImage} />

      {imgTmp !== null ? (
        <DynamicCollage width={400} height={400} images={imgTmp} matrix={[1]} />
      ) : null}
    </View>
  );
};

Answer 1

ImagePicker.showImagePicker不会返回Promise，因此等待它将无法按预期进行。

您可以做的是用Promise包装它：

  const chooseImage = async () => {
    try {
      const img = await new Promise((resolve, reject) => {
        ImagePicker.showImagePicker('', r => {
          if (r.uri) {
            const img = {uri: r.uri};
            resolve(img);
          }
          reject("uri undefined");
        });
      });
      setImgTmp(img);
      alert('...');
    } catch(e) {
     // handle exception
     console.log(e);
    }
  };

我的异步功能未正确运行

1 个答案: