如何在Android上使用phonegap/cordova下载和保存文件

Question

我在我的最后.我会尽量保持简短.使用Cordova/Phonegap 3.0(并在2.8.0上获得相同的结果).Android版本4.0.4.代码适用于BlackBerry10(Q10和Z10).

在Android上,它出现JSON错误(不,我没有解析JSON,这似乎来自cordova的大脑).我将在此末尾粘贴JSON.stringified错误对象.

那么,代码然后:首先是一个文件系统成功函数:

function onFSSuccess(fileSystem) {
if (fileSystem == null) {
    window.alert("fileSystem is null");
}
var root = fileSystem.root; 
root.getDirectory("com.app.id",{create:true},gotDir,onError);};

然后是一个处理目录检索成功的函数:

function gotDir(d){
    DATADIR = d;        
    doTheDl (d.fullPath + "/update.sql",fileTransfer);
};

然后实际调用获取文件系统:

window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, onFSSuccess, null);

然后是一个下载文件的函数:

function doTheDl (localPath,fileTransfer) {
    try {
        window.alert ("Downloading to '" + localPath + "'");
        fileTransfer.download (
            uri,
            localPath,
            function (entry) {
                try {
                    $("#dbDownloadProgressContainer").text("File saved to " + entry.name + ". Applying script to database...");
                    dbInitObj.applyUpdateScript(entry); 
                }
                catch (e) {
                    window.alert ( e);
                }

            },
            function (err) {
                window.alert ("ERROROR!!! - " + err);
                var errCodeName = err.code;
                switch (err.code) {
                    case FileTransferError.FILE_NOT_FOUND_ERR:
                        errCodeName ='FILE_NOT_FOUND_ERR';
                        break;
                    case FileTransferError.INVALID_URL_ERR:
                        errCodeName="INVALID_URL_ERR";
                        break;
                    case FileTransferError.CONNECTION_ERR:
                        errCodeName="CONNECTION_ERR";
                        break;
                    case FileTransferError.ABORT_ERR:
                        errCodeName="ABORT_ERR";
                        break;
                    default:
                        errCodeName = "UNKNOWN";
                        break;                      
                }
                window.alert ("Download failed: " + err.source + ", " + err.target + ", " + errCodeName);
            },
            true                
        );

    }
    catch (e) {
        window.alert ( e);
    }
}

男人,必须喜欢所有这些异步回调......接下来我们了解问题的核心,尝试阅读下载的文件:

//Bulk of applyUpdateScript script ommited, but eventually it gets here:

function readComplete (evt) {

    $("#dbDownloadProgressContainer").text("Parsing script file...");

    //Got this gem from here: http://beckism.com/2010/09/splitting-lines-javascript/
    var lines = evt.target.result.match(/^.*([\n\r]+|$)/gm);


    //var lineIndx = lines.length;

    window.setTimeout(function () {
            $("#dbDownloadProgressContainer").text("Processing " + lines.length + " statements");
},50);
};  

try {
        var fileReader = new FileReader();
        fileReader.onloadend=readComplete;

        fileReader.onerror=function (err) {
            //var errStr = translateFileError (err);
            window.alert ("FileReader.onerror: " +JSON.stringify (err));
        };


        fileReader.onloadstart=function (evt) {
            window.alert ("FileReader.onloadstart - " + JSON.stringify (evt));
        };


        fileReader.onload=function (evt)
        {
            window.alert ("FileReader.onload - Called when the read has successfully completed.- " + JSON.stringify (evt));
        };


        fileReader.onprogress = function (evt)
        {
            window.alert ("FileReader.onprogress - " + JSON.stringify (evt));
        }

        fileReader.onabort = function (evt)
        {
            window.alert ("FileReader.onabort - " + JSON.stringify (evt));
        }


        function gotFile (fileEntry) {
            window.alert ("Activating reader for file '" + fileEntry.fullPath + "'");
            fileReader.readAsText(fileEntry);

        };

        function noFileFound (fileError) {
            alert ("Can not access database update script: code " + translateFileError (fileError));
        };

        // window.alert ("scriptPath.name = " + scriptPath.name);

        DATADIR.getFile (scriptPath.name,null,gotFile,noFileFound);
    }
    catch (e) {
        window.alert (e);
}

现在,当我点击读取位时,我最终从'onerror'事件得到这个(rember这是JSON.stringfied错误对象:

{
   "type":"error",
   "bubbles":false,
   "cancelBubble":false,
   "cancelable":false,
   "lengthComputable":false,
   "loaded":0,
   "total":0,
   "target":{
      "_readyState":2,
      "_error":{
         "code":"JSON error"
      },
      "_result":null,
      "_fileName":"file:///mnt/sdcard/com.app.id/update.sql",
      "_realReader":{
         "error":null,
         "result":"",
         "readyState":0
      }
   }
}

另请注意,'com.app.id'是实际应用ID的占位符 - 由于担心敏感名称而无法粘贴.我也尝试过其他文件夹名称.其他值得注意的(？)项目:

• 下载进度事件似乎表明我们正在下载两倍的实际文件大小(wtf？)
• Android设备和模拟器上的结果是相同的
• BlackBerry10似乎工作正常

在此先感谢任何聪明的人......

Answer 1

好.这是解决方案:

    function gotFile (fileEntry) {
        fileEntry.file (function (file) {
        fileReader.readAsText(file);
    });
};

所以感谢BAJILLION这个家伙:http://www.html5rocks.com/en/tutorials/file/filesystem/？MoviePagespeed = noscript

如果你错过了它,神奇的是调用fileEntry对象上的"file(...)"函数.为什么它在没有它的BB10上工作.... aarrgggghhh