Question

请提供以下内容： 1. SDK版本：36 2.平台（Android / iOS / web / all）：全部

我正在开发一个react-native应用程序，我想在网络和本机上获取摄像机类型（前后）。

Camera.getAvailableCameraTypesAsync(): string[] 返回摄像机类型列表['front', 'back']。这对于仅具有前置摄像头的桌面浏览器很有用。
import { Camera } from 'expo-camera';

const types = await Camera.getAvailableCameraTypesAsync();

这是我的Camera.js：

import React, { useState, useEffect } from 'react';
import { Platform, View, TouchableOpacity } from 'react-native';
import { FAB, Text } from 'react-native-paper';
import { Camera } from 'expo-camera';

export default function CoreCamera() {
  const [hasPermission, setHasPermission] = useState(null);
  const [type, setType] = useState(Camera.Constants.Type.back);
  const [types, setTypes] = useState(null);
  useEffect(() => {
    (async () => {
      const types = await Camera.getAvailableCameraTypesAsync();
      alert(JSON.stringify(types));
      setTypes(types);
      if (Platform.OS === 'web') {
        setHasPermission(true);
      } else {
        const { status } = await Camera.requestPermissionsAsync();
        setHasPermission(status === 'granted');
      }
    })();
  }, []);

  if (hasPermission === null) {
    return <View />;
  }
  if (hasPermission === false) {
    return <Text>No access to camera</Text>;
  }

  return (
    <View style={{ flex: 1 }}>
      <Camera style={{ flex: 1 }} type={type}>
        <View
          style={{
            flex: 1,
            backgroundColor: 'transparent',
            flexDirection: 'row',
          }}
        >
          <TouchableOpacity
            style={{
              flex: 0.1,
              alignSelf: 'flex-end',
              alignItems: 'center',
            }}
            onPress={() => {
              setType(
                type === Camera.Constants.Type.back
                  ? Camera.Constants.Type.front
                  : Camera.Constants.Type.back,
              );
            }}
          >
            <FAB
              style={{ marginBottom: 20 }}
              icon="camera-switch"
            />
          </TouchableOpacity>
        </View>
      </Camera>
    </View>
  );
}

在Android上，它给我以下错误：

[Unhandled promise rejection: Error: The method or property expo-camera.getAvailableCameraTypesAsync is not available on android, are you sure you've linked all the native dependencies properly?]

在iOS上，它给我以下错误：

[Unhandled promise rejection: Error: The method or property expo-camera.getAvailableCameraTypesAsync is not available on ios, are you sure you've linked all the native dependencies properly?]

在网络上，它给我以下错误：

bundle.js:73612 Uncaught (in promise) TypeError: Cannot read property 'getAvailableCameraTypesAsync' of undefined
    at getAvailableCameraTypesAsync$ (bundle.js:73612)
    at tryCatch (bundle.js:185959)

我尝试替换：

-import { Camera } from 'expo-camera';
+import Camera from 'expo-camera/build/Camera';

现在，警报显示网络上的一个空数组。

如何使用Expo来测试网络上后置摄像头的存在？

expo-camera版本8.0.0

修改

我尝试更新expo-camera@8.2.0，这很糟糕：

Answer 1

请记住，您必须检查Web浏览器中是否可用。同样在expo docs上说它仅在网络上有效，错误消息告诉您。您可以使用：

import { Camera } from 'expo-camera';

if (await Camera.isAvailableAsync()) {
    const types = await Camera.getAvailableCameraTypesAsync();
    // save values into on types
}

您可以在组件的useEffect函数中使用此函数来进行查找。对不起，英语不好：。

Camera.getAvailableCameraTypesAsync（）在网络和本机上不起作用

1 个答案: