Question

我对内部存储没有问题，但我想在外部SD卡上创建一个目录，其中包含KitKat之前的版本File.mkdirs()。

我的部分代码是：

//external sd card
DocumentFile.fromFile(new File("/storage/sdcard1/")).exists(); //returns true
DocumentFile.fromFile(new File("/storage/sdcard1/")).canRead(); //returns true
DocumentFile.fromFile(new File("/storage/sdcard1/")).canWrite(); //returns true
DocumentFile.fromFile(new File("/storage/sdcard1/test")).exists(); //returns false
DocumentFile.fromFile(new File("/storage/sdcard1/")).createDirectory("test"); //returns null

//internal storage
DocumentFile.fromFile(new File("/storage/emulated/0/")).exists(); //returns true
DocumentFile.fromFile(new File("/storage/emulated/0/test")).exists(); //returns false
DocumentFile.fromFile(new File("/storage/emulated/0/")).createDirectory("test"); //it works
DocumentFile.fromFile(new File("/storage/emulated/0/test")).exists(); //returns true
DocumentFile.fromFile(new File("/storage/emulated/0/test")).createFile("text", "file.txt"); //it works

//external sd card
(new File("/storage/sdcard1/test2/subfolder")).exists(); //returns false
(new File("/storage/sdcard1/test2/subfolder")).mkdirs(); //returns false

//internal storage
(new File("/storage/emulated/0/test2/subfolder")).exists(); //returns false
(new File("/storage/emulated/0/test2/subfolder")).mkdirs(); //returns true

在AndroidManifest.xml中：

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

使用BQ Aquaris e4，Android Lollipop 5.0和1GB micro SD卡进行测试。

更新：这是我获取卷列表的方式：

private static ArrayList<StorageInfo> listAvaliableStorage(Context context) {
        ArrayList<StorageInfo> storagges = new ArrayList<>();
        StorageManager storageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
        try {
            Class<?>[] paramClasses = {};
            Method getVolumeList = StorageManager.class.getMethod("getVolumeList", paramClasses);
            getVolumeList.setAccessible(true);
            Object[] params = {};
            Object[] invokes = (Object[]) getVolumeList.invoke(storageManager, params);
            if (invokes != null) {
                StorageInfo info;
                for (Object obj : invokes) {
                    Method getPath = obj.getClass().getMethod("getPath");
                    String path = (String) getPath.invoke(obj);
                    info = new StorageInfo(path);
                    File file = new File(info.getPath());
                    if ((file.exists()) && (file.isDirectory())
                        //&& (file.canWrite())
                            ) {
                        info.setTotalStorage(file.getTotalSpace());
                        info.setFreeStorage(file.getUsableSpace());
                        Method isRemovable = obj.getClass().getMethod("isRemovable");
                        String state;
                        try {
                            Method getVolumeState = StorageManager.class.getMethod("getVolumeState", String.class);
                            state = (String) getVolumeState.invoke(storageManager, info.getPath());
                            info.setState(state);
                            info.setRemovable((Boolean) isRemovable.invoke(obj));
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                        storagges.add(info);
                    }
                }
            }
        } catch (NoSuchMethodException | IllegalArgumentException | IllegalAccessException | InvocationTargetException e) {
            e.printStackTrace();
        }
        storagges.trimToSize();

        return storagges;
    }

硬编码路径仅适用于此示例

更新2：我已经在SD卡中使用文件浏览器创建了目录：“test”。当我执行此代码时：

File file = new File("/storage/sdcard1/test/", "file.txt");
fileOutput = new FileOutputStream(file);

第二行抛出FileNotFoundException: /storage/sdcard1/test/file.txt: open failed: EACCES (Permission denied)

我做错了什么？

Answer 1

这是由于Android Lollipop的设计。 Environment.getExternalStorageDirectory()将仅返回模拟外部存储的路径。 Android不公开任何能为您提供SD卡路径的API。

此外，在Lollipop中，除非通过Storage Access Framework获得用户权限，否则应用程序无法写入sdcard中自己目录之外的位置。

试试context.getExternalFilesDirs()。这会为您提供应用可以将数据写入的路径列表。其中一个将在SD卡中，并将像/ storage / sdcardname / Android / data / yourAppName / files

Answer 2

你必须明确定义位置，这里是我创建文件夹和文件夹内的文件夹的短脚本，希望这有帮助

    import java.io.File;
    import android.app.Activity;
    import android.content.Context;
    import android.os.Bundle;
    import android.os.Environment;
    import android.widget.Toast;

public class DirectoryPicker extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.chooser_list);//your xml layout file name
}
@Override
public void onStart() {
    super.onStart();
    String state = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED.equals(state)) { // **Check that we have access to create the folder(s)**
        File Root = Environment.getExternalStorageDirectory(); //**Get the path and hold it**
//**Alternativly you can select a certain directory with**
//File Root = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        File folder = new File(Root.getAbsolutePath() + "/main_folder_to_add/second_folder/");//**This puts everything together CORRECTLY**
        folder.mkdirs();//**Makes the directory folders, make sure to use mkdirs not mkdir**
        if (!folder.exists()) {
            folder.mkdirs();
        }
        Context context = getApplicationContext();//**Prove we were successful**
        String msg = folder.toString();
        Toast toast = Toast.makeText(context, msg, Toast.LENGTH_LONG);
        toast.show();
        return;
    }
}
public void onBackPressed() {

finish();
}
}

无法在外部SD卡（Lollipop）中创建目录

2 个答案: