列出Android手机下载目录中的文件

Question

我使用以下代码尝试列出下载目录中的文件.

我构建了apk,将其安装在我的手机上,然后运行它.当我在手机的文件浏览器中查看时,我在内存/下载文件夹和外部存储器/下载文件夹中都有文件,但应用程序不显示文件列表.当我调试时,我发现该listFiles()函数返回null.

请让我知道我做错了什么.变量的state值已安装,因此该问题与未安装的内存无关.

String state = Environment.getExternalStorageState();

private boolean isMediaAvailable() {

    if (Environment.MEDIA_MOUNTED.equals(state)) {
        return true;
    } else {
        return false;
    }
}


if (!isMediaAvailable()) {
        Utility.finishWithError(this,"Media Not Available");
    } else {

        String path =Environment.getExternalStorageDirectory().toString()+ File.separator + Environment.DIRECTORY_DOWNLOADS;



        File file = new File(path);
        mRootPath = file.getAbsoluteFile().getPath();



        mFileNames = new ArrayList<String>();

        File filesInDirectory[] = file.listFiles();


        if (filesInDirectory != null) {
            for (int i = 0; i<filesInDirectory.length;i++) {
                    mFileNames.add(filesInDirectory[i].getName());
            }
        }

    }

Answer 1

使用 :

Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)

获取下载的目录,

并使用File.list()获取包含目录中文件列表的数组.

Answer 2

为您的项目清单文件添加存储权限：

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

并要求用户授予这样的权限：

int PERMISSION_ALL = 1;
String[] PERMISSIONS = {android.Manifest.permission.READ_EXTERNAL_STORAGE, android.Manifest.permission.WRITE_EXTERNAL_STORAGE};

将此方法添加到您的代码中：

public static boolean hasPermissions(Context context, String... permissions) {
    if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
        for (String permission : permissions) {
            if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                return false;
            }
        }
    }
    return true;
}

并且可以选择覆盖它：

    @Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    switch (requestCode) {
        case 1: {

            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.
                Toast.makeText(getApplicationContext(), "permission was granted", Toast.LENGTH_SHORT).show();

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
                Toast.makeText(getApplicationContext(), "Permission denied", Toast.LENGTH_SHORT).show();
            }
            return;
        }
    }
}

现在您可以使用以下代码访问您的应用程序下载目录：

context.getApplicationContext().getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS);

祝你好运 ：）