详解react-native-fs插件的使用以及遇到的坑

npm install react-native-fs --save
//注意：如果react native版本是<0.40安装，使用此标签：
npm install react-native-fs@2.0.1-rc.2 --save 

react-native link react-native-fs 

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />　 

downloadFile(imageId, cookie, callback) {

    const downloadDest = `${RNFS.DocumentDirectoryPath}/${((Math.random() * 1000) | 0)}.jpg`;

    var formUrl = CommonSvc.baseURL + '/api/image/0/' + imageId;

    //var formUrl = 'http://lorempixel.com/400/200/';

    const options = {

      fromUrl: formUrl,

      toFile: downloadDest,

      background: true,

      headers: {

        'Cookie': cookie //需要添加验证到接口要设置cookie

      },

      begin: (res) => {

        //console.log(res);

      },

      progress: (res) => {

        //console.log(res);

      }

    };

    try {

      const ret = RNFS.downloadFile(options);

      ret.promise.then(res => {

        //callback(null, Platform.OS === 'android' "error")

    }

 

  }, 

_appLogin(userName, password, callback){

 

    fetch(commonSvc.baseURL + '/account/app-login', {

      method: 'POST',

      headers: {

        'Accept': 'application/json',

        'Content-Type': 'application/json'

      },

      body: JSON.stringify({

        UserName: userName,

        Password: password

      })

    }).then(

      (response) => {

        if (response.ok) {

          return response;

        } else {

          var message;

          switch (response.status) {

            case 710:

              message = LanguageChooseSvc.strings['api_common_' + 710];

              break;

            case 711:

              message = LanguageChooseSvc.strings['api_common_' + 711];

              break;

            case 400:

              message = LanguageChooseSvc.strings['api_common_' + 400];

              break;

            default:

              message = commonSvc.httpErrorMessage;

              break;

          }

          throw {message: message};

        }

      }

    ).then(

      (responseJson) => {

        callback(null, responseJson);

      }

    ).catch(

      (error) => {

        callback(error.message);

      }

    );

  }, 

 downloadFile(imageId, cookie, callback) {

    const downloadDest = `${RNFS.DocumentDirectoryPath}/${((Math.random() * 1000) | 0)}.jpg`;

    var formUrl = CommonSvc.baseURL + '/api/image/0/' + imageId;

    //var formUrl = 'http://lorempixel.com/400/200/';

    const options = {

      fromUrl: formUrl,

      toFile: downloadDest,

      background: true,

      headers: {

        'Cookie': cookie //需要添加验证到接口要设置cookie

      },

      begin: (res) => {

        //console.log(res);

      },

      progress: (res) => {

        //console.log(res);

      }

    };

    try {

      const ret = RNFS.downloadFile(options);

      ret.promise.then(res => {

        //callback(null, Platform.OS === 'android' "error")

    }

 

  },