Question

我想检查Android中的“下载”文件夹中是否已存在该文件。我使用Android下载管理器下载文件。在那里if部分不起作用。如果文件已存在（例如：文件名 - songname.mp3），则第二次下载同一文件时，它会将文件下载为songname1.mp3。我试过下面的代码。如果文件已经存在，我想显示一条消息。

请帮我解决这个问题。

public void DownloadChecker() {
    File applictionFile =  new File(Environment.getExternalStoragePublicDirectory(
        Environment.DIRECTORY_DOWNLOADS)+ "/"+"mysongs.mp3");

    if(applictionFile.exists()) {
         Toast.makeText(getApplicationContext(), "File Already Exists", 
            Toast.LENGTH_LONG).show();
    } else {
        String servicestring = Context.DOWNLOAD_SERVICE;
        DownloadManager downloadmanager;
        downloadmanager = (DownloadManager) getSystemService(servicestring);
        Uri uri = Uri.parse(DownloadUrl);
        DownloadManager.Request request = new DownloadManager.Request(uri);
        request.setDestinationInExternalFilesDir(MainActivity.this,
            Environment.DIRECTORY_DOWNLOADS,"mysongs.mp3");

        Long reference = downloadmanager.enqueue(request);
    }
}

Answer 1

您应该尝试更改：

File applictionFile =  new File(Environment.
        getExternalStoragePublicDirectory(Environment
                .DIRECTORY_DOWNLOADS)+ "/"+"mysongs.mp3");

为：

File applictionFile =  new File(Environment.
        getExternalStoragePublicDirectory(Environment
                .DIRECTORY_DOWNLOADS).getAbsolutePath() + "/" + "mysongs.mp3");

Answer 2

您在哪个测试设备上测试您的应用？它是否在api-23之上，那么你应该在运行时设置权限！或者试试这个

File extStore = Environment.getExternalStorageDirectory();
File myFile = new File(extStore.getAbsolutePath() + "/mysongs.mp3");

if(myFile.exists()){
    Toast.makeText(getApplicationContext(), "File Already Exists", 
        Toast.LENGTH_LONG).show();
}

Answer 3

更改

 if(applictionFile.exists()) {
         Toast.makeText(getApplicationContext(), "File Already Exists", 
            Toast.LENGTH_LONG).show();
    }

以

if(applictionFile.canRead()) { Toast.makeText(getApplicationContext(), "File Already Exists", Toast.LENGTH_LONG).show(); }

或

if(applictionFile.isFile()) { Toast.makeText(getApplicationContext(), "File Already Exists", Toast.LENGTH_LONG).show(); }

Answer 4

以简单的方式尝试

File f = new File(filePathString);
if(f.exists() && !f.isDirectory()) { 
    // do your code stuff
}

检查文件是否已存在Android无效

4 个答案: