FileReader (cordova-plugin-file)失败

Question

我正在尝试使用cordova- plugin -file插件来读写文件。写入文件似乎工作得很好，但是当我读取文件时，它不工作，并且我设置的失败回调运行。

function getData(fetch) {
    alert('Getting data')
    window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {
    fs.root.getFile(department + ".txt", { create: false, exclusive: false }, function (fileEntry) {
        alert('reading this file: ' + JSON.stringify(fileEntry))
        readFile(fileEntry);
    }, addDepartment);
    });

    if (typeof sessionStorage.currentGroup != 'undefined') {groupData = dataActive[sessionStorage.currentGroup];}
    if (typeof sessionStorage.currentSubgroup != 'undefined') {subgroupData = groupData[sessionStorage.currentSubgroup];}
    if (typeof sessionStorage.currentItem != 'undefined') {itemData = subgroupData[sessionStorage.currentItem];}
    if (typeof itemData != 'undefined') {
    UCC = itemData.UCC;
    GTIN = itemData.GTIN;
    ProductionDate = itemData.ProductionDate;
    Weight = itemData.Weight;
    SerialNum = itemData.SerialNum;
    }
    fetch();
}


function readFile(fileEntry) {
    alert('Reading file')

    fileEntry.file(function (file) {
        var reader = new FileReader();

        reader.onloadend = function() {
            console.log("Successful file read: " + this.result);
            window.dataActive = JSON.parse(this.result);
            alert('dataActive was read as: ' + dataActive)
            displayFileData(fileEntry.fullPath + ": " + this.result);
        };
        reader.readAsText(file);

    }, alert('failed to read file!'));
}

我一直收到“无法读取文件”的消息，其余的代码无法运行，因为没有数据(我需要从文件中获取数据)。我对JavaScript和PhoneGap/Cordova还不太熟悉，

更新

我试图调试我的代码，因为它充满了问题，但现在我降到了最低限度，我已经仔细检查了所有东西，但我仍然不知道问题是什么。我已经非常仔细地遵循了文档示例(https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-file/)，但它就是不能工作。当它读取文件时，我一直得到null。我的代码如下：

window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {

    fs.root.getFile("newPersistentFile.txt", { create: true, exclusive: false }, function (fileEntry) {
        alert(JSON.stringify(fileEntry))
        // fileEntry.name == 'someFile.txt'
        // fileEntry.fullPath == '/someFile.txt'
        writeFile(fileEntry, 'sample text');
        readFile(fileEntry);

    }, function() {alert('onErrorCreateFile')});

}, function() {alert('onErrorLoadFs')});

function readFile(fileEntry) {

    fileEntry.file(function (file) {
        var reader = new FileReader();

        reader.onloadend = function() {
            console.log("Successful file read: " + this.result);
            //displayFileData(fileEntry.fullPath + ": " + this.result);
        };

        reader.readAsText(file);

    }, function() {alert('onErrorReadFile')});
}

function writeFile(fileEntry, dataObj) {
    // Create a FileWriter object for our FileEntry (log.txt).
    fileEntry.createWriter(function (fileWriter) {

        fileWriter.onwrite = function() {
            alert("Successful file write...");
            readFile(fileEntry);
            alert('Contents are: ' + this.result);
        };

        fileWriter.onerror = function (e) {
            alert("Failed file write: " + e.toString());
        };

        fileWriter.write(dataObj);
    });
}

Answer 1

您正在使用的参数与内部的函数不同。您的代码应如下所示：

function readFile(fileEntry) {
    alert('Reading file')

    fileEntry.file(function (fileEntry) {
        var reader = new FileReader();

        reader.onloadend = function() {
            console.log("Successful file read: " + this.result);
            window.dataActive = JSON.parse(this.result);
            alert('dataActive was read as: ' + dataActive)
            displayFileData(fileEntry.fullPath + ": " + this.result);
        };
        reader.readAsText(fileEntry);

    }, alert('failed to read file!'));
}

Answer 2

我终于明白了！老实说，我不确定我一开始做错了什么，但在旋转了我的轮子似乎很长一段时间后，我终于让它工作了。这是我的代码。这只是一个示例，所以它实际上不会做任何有用的事情，但是如果有人遇到了同样的问题，希望这也能帮助他们，他们可以根据需要进行编辑。

window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {

    fs.root.getFile("newPersistentFile2.txt", { create: true, exclusive: false }, function (fileEntry) {
        // fileEntry.name == 'someFile.txt'
        // fileEntry.fullPath == '/someFile.txt'
        //var sample = new Blob(['some file data'], { type: 'text/plain' }); this works too or you can just use ['some file data'] like below
        writeFile(fileEntry, ['some file data']);

    }, function() {alert('onErrorCreateFile')});

}, function() {alert('onErrorLoadFs')});

function readFile(fileEntry) {

    fileEntry.file(function (file) {
        var reader = new FileReader();

        reader.onload = function() {
            alert("Successful file read: " + this.result);
            //displayFileData(fileEntry.fullPath + ": " + this.result);
        };

        reader.readAsText(file);

    }, function() {alert('onErrorReadFile')});
}

function writeFile(fileEntry, dataObj) {
    // Create a FileWriter object for our FileEntry (log.txt).
    fileEntry.createWriter(function (fileWriter) {

        fileWriter.onwrite = function() {
            alert("Successful file write...");
            readFile(fileEntry);
        };

        fileWriter.onerror = function (e) {
            alert("Failed file write: " + e.toString());
        };

        fileWriter.write(dataObj);
    });
}