Android 不允许使用 SDK 更新创建目录

Question

奇怪的问题，但在一台设备上 Android 不再允许应用程序创建目录（或任何目录）。这似乎发生在我移动到 SDK 27 之后（我引入了一个需要升级的第三方库）。更奇怪的是，它适用于其他设备。不工作的设备是 Samsung Galaxy Tab S3，运行 Android 8 (sdk 26)。

这是失败的代码：

public static String mediaStorageDirectory() {
    return Environment.getExternalStorageDirectory().toString() + File.separator + "myapp";
}

private DatabaseHelper(Context context) {
    super(context, DB_NAME, null, 1); 
    File dbPath = new File(Utilities.mediaStorageDirectory() + "/databases/");
    if (!dbPath.exists()) {
        if (dbPath.mkdirs()) {
            this.mContext = context;
            createDataBase();
        }
    }
}

代码创建一个目录，然后将应用程序数据库复制到该目录中。此代码从一开始就一直有效...是否 Android 更改了文件创建的一些安全要求？

如果你想知道，我已经设置了如下权限：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

并在创建目录结构之前提示用户成功获得这些权限。

Answer 1

所以问题似乎与 SDK 27 有关。他们现在似乎要求（强制？）授予 WRITE 的权限。以前只需要 READ。我假设这与安全升级有关，但我找不到有关此更改的任何文档。也许其他人之前只是做了包含。对于那些想查看执行权限处理的代码的人，我不久前从另一个 Stack Overflow 中提取了以下代码。我只是添加了之前缺少的 WRITE_EXTERNAL_STORAGE 部分：

final private int REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS = 124;

public void checkPermissions() {
    List<String> permissionsNeeded = new ArrayList<String>();

    final List<String> permissionsList = new ArrayList<String>();
    if (!addPermission(permissionsList, Manifest.permission.CAMERA))
        permissionsNeeded.add("Camera");
    if (!addPermission(permissionsList, Manifest.permission.READ_EXTERNAL_STORAGE))
        permissionsNeeded.add("Read External Storage");
    if (!addPermission(permissionsList, Manifest.permission.WRITE_EXTERNAL_STORAGE))
        permissionsNeeded.add("Write External Storage");
    if (!addPermission(permissionsList, Manifest.permission.ACCESS_FINE_LOCATION))
        permissionsNeeded.add("GPS");
    if (!addPermission(permissionsList, Manifest.permission.RECORD_AUDIO))
        permissionsNeeded.add("Record Audio");

    if (permissionsList.size() > 0) {
        if (permissionsNeeded.size() > 0) {
            // Need Rationale
            String message = "You need to grant access to " + permissionsNeeded.get(0);
            for (int i = 1; i < permissionsNeeded.size(); i++) {
                message = message + ", " + permissionsNeeded.get(i);
            }

            message = message + "." + " If you do not the application may not function correctly.";

            showMessageOKCancel(message, this,
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            requestPermissions(permissionsList.toArray(new String[permissionsList.size()]),
                                    REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
                        }
                    });
        } else {
            requestPermissions(permissionsList.toArray(new String[permissionsList.size()]),
                    REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
        }
    }
}

private static void showMessageOKCancel(String message, Activity activity, DialogInterface.OnClickListener okListener) {
    new AlertDialog.Builder(activity).setMessage(message).setPositiveButton("OK", okListener).create().show();
}

private boolean addPermission(List<String> permissionsList, String permission) {
    if (checkSelfPermission(permission) != PackageManager.PERMISSION_GRANTED) {
        permissionsList.add(permission);
        // Check for Rationale Option
        if (!shouldShowRequestPermissionRationale(permission))
            return false;
    }
    return true;
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS: {
            Map<String, Integer> perms = new HashMap<String, Integer>();
            // Initial
            perms.put(Manifest.permission.ACCESS_FINE_LOCATION, PackageManager.PERMISSION_GRANTED);
            perms.put(Manifest.permission.CAMERA, PackageManager.PERMISSION_GRANTED);
            perms.put(Manifest.permission.RECORD_AUDIO, PackageManager.PERMISSION_GRANTED);
            perms.put(Manifest.permission.READ_EXTERNAL_STORAGE, PackageManager.PERMISSION_GRANTED);
            perms.put(Manifest.permission.WRITE_EXTERNAL_STORAGE, PackageManager.PERMISSION_GRANTED);
            // Fill with results
            for (int i = 0; i < permissions.length; i++)
                perms.put(permissions[i], grantResults[i]);
            // Check for ACCESS_FINE_LOCATION
            if (perms.get(Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
                    && perms.get(Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED
                    && perms.get(Manifest.permission.RECORD_AUDIO) == PackageManager.PERMISSION_GRANTED
                    && perms.get(Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED
                    && perms.get(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
                // All Permissions Granted
            }
            // Warn the user that the application will not run
            else if (perms.get(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                AlertDialog.Builder builder = new AlertDialog.Builder(StartActivity.this);
                builder.setTitle("File Read Permissions Not Granted");
                builder.setMessage("The Application cannot operate without READ access to files on your device. Do you want to grant this access?");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCompat.requestPermissions(StartActivity.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 0);
                    }
                });
                builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {

                    }
                });
                if (!isFinishing())
                    builder.show();
            }
            // Warn the user that the application will not run
            else if (perms.get(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                AlertDialog.Builder builder = new AlertDialog.Builder(StartActivity.this);
                builder.setTitle("File Write Permissions Not Granted");
                builder.setMessage("The Application cannot operate without WRITE access to directories on your device. Do you want to grant this access?");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCompat.requestPermissions(StartActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 0);
                    }
                });
                builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {

                    }
                });
                if (!isFinishing())
                    builder.show();
            }else {
                // Permission Denied
                Toast.makeText(StartActivity.this, "Some Permission is Denied", Toast.LENGTH_SHORT)
                        .show();
            }
        }
        break;
        default:
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

该调用是特定于 SDK 的，已添加到主 activity:

的 OnCreate()

    // Check permissions for Android 6.0 devices
    if (Build.VERSION.SDK_INT >= 23) {
        // Marshmallow+
        checkPermissions();
    }

Android 不允许使用 SDK 更新创建目录

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