Question

I am using phonegap file reading functionality, once i read the content and i will do some functionality with that content, once that over i am calling file truncate functionality. In that i can’t truncate any value. Help me to fix this issue.

removeFileContent();

function removeFileContent(){
    console.log("Inside remove file content");
    window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, gotFileTruncate, onProcessFailure);
};

function gotFileTruncate(fileSystem){
    console.log("Inside get file path for remove content");
    /** Function to get file path */
    filePath = getFilePath(device.platform);
    console.log("Device File Path to remove content-->"+this.filePath);
    fileSystem.root.getFile(filePath, null, gotFileEntryTruncate, onProcessFailure);
}

function gotFileEntryTruncate(fileEntry){
    globals.raiseLog("Inside file to truncate call");
    globals.raiseLog("File Name-->"+fileEntry.name);
    fileEntry.createWriter(gotFileWriter, onProcessFailure);
}

function gotFileWriter(writer){
    globals.raiseLog("Inside file writer to truncate file content");
    globals.raiseLog("Content length-->"+writer.length);
    //writer.truncate(10);
    writer.onwriteend = function(evt) {
        writer.truncate(0);
        writer.onwriteend = function(evt) {
        };
    };
    writer.write("");
    globals.raiseLog("Content length after truncate-->"+writer.length);
}

In the above gotFileWriter() if i check for writer.length its still showing some count. I dont know how come we can check the file gets empty. I having some text inside that file. Need to clear the file when i finish the reading of the file. I am calling removeFileContent() after i finish the reading functionality. Kindly help.

Answer 1

The way your code is written you may get a false positive that the file still has contents in it. Move your:

globals.raiseLog("Content length after truncate-->"+writer.length);

into your onwriteend function as the write call is async and may not finish before your log is printed.