Android M写入SD卡 - 权限被拒绝

Question

我正在尝试将文件从我的应用程序中复制到SD卡,但我得到错误eacces(权限被拒绝).操作系统是Android M,我已经允许运行时存储权限(在应用信息中检查).我还在AndroidManifest.xml中设置了uses-permission

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

如果我复制到SD卡不起作用

Source: data/user/0/com.example.myapp/cache/SomeFile.txt
Destination: /storage/1032-2568/SomeFolder/
Error: java.io.FileNotFoundException: /storage/1032-2568/SomeFolder/SomeFile.txt: open failed: EACCES (Permission denied)

如果我复制到内部存储,则有效

Source: data/user/0/com.example.myapp/cache/SomeFile.txt
Destination: /storage/emulated/0/SomeFolder/

将文件从源复制到目标的代码

/*
 * Below are the parameters I have tried
 *
 * inputPath - data/user/0/com.example.myapp/cache or data/user/0/com.example.myapp/cache/
 * inputFile - /SomeFile.txt or SomeFile.txt
 * outputPath - /storage/1032-2568/SomeFolder/ or /storage/1032-2568/SomeFolder
 */
public static void copyFile(String inputPath, String inputFile, String outputPath) {

    InputStream in = null;
    OutputStream out = null;
    try {

        //create output directory if it doesn't exist
        File dir = new File (outputPath);
        if (!dir.exists()) {
            dir.mkdirs();
        }

        in = new FileInputStream(inputPath + inputFile);
        out = new FileOutputStream(outputPath + inputFile);

        byte[] buffer = new byte[1024];
        int read;
        while ((read = in.read(buffer)) != -1) {
            out.write(buffer, 0, read);
        }
        in.close();


        // write the output file (You have now copied the file)
        out.flush();
        out.close();
    }
    catch (FileNotFoundException fnfe1) {
        /* I get the error here */
        Log.e("tag", fnfe1.getMessage());
    }
    catch (Exception e) {
        Log.e("tag", e.getMessage());
    }
}

ES文件浏览器

我看到ES File Explorer也无法在Redmi设备上的SD卡上写任何东西.这是一个带解决方案的视频.按照我的设备上的ES Explorer的步骤.这可以通过编程方式完成吗？

Answer 1

正如@CommonsWare所建议的那样,我们必须使用android提供的新的存储访问框架,并且必须获得用户的许可才能编写SD卡文件,如您所说,这已经在文件管理器应用程序ES文件资源管理器中编写.

以下是允许用户选择"SD卡"的代码:

startActivityForResult(new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE), requestCode);

看起来有点像这样:

并获取Document path pickedDir并在copyFile块中进一步传递并使用此路径写入文件:

public void onActivityResult(int requestCode, int resultCode, Intent resultData) {
    if (resultCode != RESULT_OK)
        return;
    else {
        Uri treeUri = resultData.getData();
        DocumentFile pickedDir = DocumentFile.fromTreeUri(this, treeUri);
        grantUriPermission(getPackageName(), treeUri, Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        getContentResolver().takePersistableUriPermission(treeUri, Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        copyFile(sdCard.toString(), "/File.txt", path + "/new", pickedDir);
    }
}


public void copyFile(String inputPath, String inputFile, String outputPath, DocumentFile pickedDir) {

    InputStream in = null;
    OutputStream out = null;
    try {

        //create output directory if it doesn't exist
        File dir = new File(outputPath);
        if (!dir.exists()) {
            dir.mkdirs();
        }

        in = new FileInputStream(inputPath + inputFile);
        //out = new FileOutputStream(outputPath + inputFile);

        DocumentFile file = pickedDir.createFile("//MIME type", outputPath);
        out = getContentResolver().openOutputStream(file.getUri());

        byte[] buffer = new byte[1024];
        int read;
        while ((read = in.read(buffer)) != -1) {
            out.write(buffer, 0, read);
        }
        in.close();


        // write the output file (You have now copied the file)
        out.flush();
        out.close();
    } catch (FileNotFoundException fnfe1) {
    /* I get the error here */
        Log.e("tag", fnfe1.getMessage());
    } catch (Exception e) {
        Log.e("tag", e.getMessage());
    }
}

Answer 2

您需要在Android 6.0(API Level 23)及更高版本中添加权限请求运行时,这是官方文档

这是代码 WRITE_EXTERNAL_STORAGE

if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    Log.d(TAG,"Permission is granted");

    return true;
}

请求这样的许可

ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);