如何在android中以编程方式更改文件/文件夹权限

Question

如果正在存储应用程序数据库，我想更改文件夹的权限。

在谷歌上搜索后发现：-

public int chmod(File path, int mode) throws Exception {
  Class fileUtils = Class.forName("android.os.FileUtils");
  Method setPermissions =
      fileUtils.getMethod("setPermissions", String.class, int.class, int.class, int.class);
  return (Integer) setPermissions.invoke(null, path.getAbsolutePath(), mode, -1, -1);
}

...
chmod("/foo/bar/baz", 0755);
...

这里的 FileUtils 类应该是 android.os 包的一部分，但我在导入包时找不到它。

知道如何使用FileUtils 或其他方式来更改文件夹的权限吗？

我正在更改权限，因为在安装我的应用程序后，当我尝试访问数据库时，应用程序停止工作。由于我的设备是rooted，所以当我使用Root Browser 将数据库文件夹的权限从771 更改为777 时，应用程序开始完美运行。

那么如何在安装应用程序时更改文件夹的权限，即在unrooted 设备中以编程方式？

我的DBHelper 班级：-

public class DBHelper extends SQLiteOpenHelper {

public SQLiteDatabase database = null;
public File databaseFile;
public static String databaseName = "Db1.sqlite";
public String databasePath = "";
Context mContext;

public DBHelper(Context paramContext) {

    super(paramContext, databaseName, null, 1);
    this.mContext = paramContext;

    Log.d("data", "package name:" + paramContext.getPackageName());

    //this.databasePath = ("data/data/" + paramContext.getPackageName() + "/databases/"+databaseName);
    this.databasePath = (Environment.getExternalStorageDirectory().getAbsolutePath()+"/Android/data/"+paramContext.getPackageName()+"/"+databaseName);
    System.out.println(databasePath);
    this.databaseFile = new File(this.databasePath);
    if (!this.databaseFile.exists())
        try {
            deployDataBase(DBHelper.databaseName, this.databasePath);
            return;
        } catch (IOException localIOException) {
            localIOException.printStackTrace();
        }
}

private void deployDataBase(String dbNAme, String dbPath)
        throws IOException {
    InputStream localInputStream = this.mContext.getAssets().open(dbNAme);
    FileOutputStream localFileOutputStream = new FileOutputStream(dbPath);
    byte[] arrayOfByte = new byte[1024];
    while (true) {
        int i = localInputStream.read(arrayOfByte);
        if (i <= 0) {
            localFileOutputStream.flush();
            localFileOutputStream.close();
            localInputStream.close();
            return;
        }
        localFileOutputStream.write(arrayOfByte, 0, i);
    }
}

@Override
public synchronized void close() {

    if (database != null)
        database.close();

    super.close();

}
@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

}

Answer 1

• 不要为您的案例使用 db 路径和文件权限。

• IMO Rooted 和普通设备是互斥的受众。

• 仅用于您的测试 root 设备在 sd 卡上创建 db，其路径源自 Environment.getExternalStorage** 方法。

将您的数据库保存在 SD 卡上。做这样的事情。

把这个类放在你的代码包中。

package com.test.db;

import java.io.File;

import android.content.Context;
import android.content.ContextWrapper;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.os.Environment;

/** 
 * Custom context wrapper to proxy the database file path.
 * Instead of storing data on internal storage for app
 * we will storing the data on external sd card.
 */
public class DatabaseContext extends ContextWrapper {

    /*
     * Used for logging.
     */
    private static final String DEBUG_CONTEXT = "DatabaseContext";

    /*
     * Constructor wrapping given app context.
     */
    public DatabaseContext(Context base) {
        super(base);
    }

    /**
     * Proxy the path to data base file for every operation
     * @see android.content.ContextWrapper#getDatabasePath(java.lang.String)
     */
    @Override
    public File getDatabasePath(String name) {

        String state = Environment.getExternalStorageState();

        if (Environment.MEDIA_MOUNTED.equals(state)) {
            // We can read and write the media
            File sdcard = Environment.getExternalStorageDirectory();
            String dbfile = sdcard.getAbsolutePath() + File.separator + "com.test" +     File.separator + "database" + File.separator
                + name;
            if (!dbfile.endsWith(".db")) {
                dbfile += ".db";
            }

            File result = new File(dbfile);

            if (!result.getParentFile().exists()) {
                if(!result.getParentFile().mkdirs()){
                    result = new File(sdcard, name);
                }
            }

            if (android.util.Log.isLoggable(DEBUG_CONTEXT, android.util.Log.WARN)) {
                android.util.Log.w(DEBUG_CONTEXT,
                    "getDatabasePath(" + name + ") = " + result.getAbsolutePath());
            }

            return result;

        } else {
            // Something else is wrong. It may be one of many other states,
            // Writing data on internal storage
            return super.getDatabasePath(name);
        }

    }

    @Override
    public SQLiteDatabase openOrCreateDatabase(String name, int mode,
            CursorFactory factory) {
        return openOrCreateDatabase(name, mode, factory, null);
    }

    @Override
    public SQLiteDatabase openOrCreateDatabase(String name, int mode, CursorFactory factory,
        DatabaseErrorHandler errorHandler) {
        SQLiteDatabase result = SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name)
            .getAbsolutePath(), null, errorHandler);

        return result;
    }
}

像这样扩展 SqliteOpenHelper 类

package com.test.db;

import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

import android.content.Context; 
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * Custom SqliteOpenHelper.
 */
public class MySQLiteOpenHelper extends SQLiteOpenHelper {

    private static final String TAG = My.class.getSimpleName();

    private final Context context;

    public  MySQLiteOpenHelper(Context context, String name, int version, String mResourceName) {
        super(new DatabaseContext(context), name, /*factory*/null, version);
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
      // Create tables here
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }

}

这是在 sd 卡中创建数据库的测试片。请检查