Android:自定義Sqlite數據庫路徑

默認的sqlite數據庫是放在/data/data/database目錄下的，今天看騰訊雲IM的demo發現再該路徑下找不到它存放消息的數據庫，找了下后發現居然是放在/data/data/files目錄下的，雖然不知道為什么要放到這個目錄，不過仔細想了下突然發覺假如把數據庫放到非data目錄下的話，就可以不借助contentprovider之類的方式實現跨應用訪問數據庫了，雖然安全性會降低，但在部分場景下還是會有所作用的。

閱讀下了SqliteOpenHelper的源碼，和數據庫路徑相關部分如下。

public SQLiteDatabase getWritableDatabase() {
        synchronized (this) {
            return getDatabaseLocked(true);
        }
    }

    
    public SQLiteDatabase getReadableDatabase() {
        synchronized (this) {
            return getDatabaseLocked(false);
        }
    }

private SQLiteDatabase getDatabaseLocked(boolean writable) {
        if (mDatabase != null) {
            if (!mDatabase.isOpen()) {
                // Darn!  The user closed the database by calling mDatabase.close().
                mDatabase = null;
            } else if (!writable || !mDatabase.isReadOnly()) {
                // The database is already open for business.
                return mDatabase;
            }
        }

        if (mIsInitializing) {
            throw new IllegalStateException("getDatabase called recursively");
        }

        SQLiteDatabase db = mDatabase;
        try {
            mIsInitializing = true;

            if (db != null) {
                if (writable && db.isReadOnly()) {
                    db.reopenReadWrite();
                }
            } else if (mName == null) {
                db = SQLiteDatabase.create(null);
            } else {
                try {
                    if (DEBUG_STRICT_READONLY && !writable) {
                       String path = mContext.getDatabasePath(mName).getPath()
                        db = SQLiteDatabase.openDatabase(path, mFactory,
                                SQLiteDatabase.OPEN_READONLY, mErrorHandler);
                    } else {
                        db = mContext.openOrCreateDatabase(mName, mEnableWriteAheadLogging ?
                                Context.MODE_ENABLE_WRITE_AHEAD_LOGGING : 0,
                                mFactory, mErrorHandler);
                    }
                } catch (SQLiteException ex) {
                    if (writable) {
                        throw ex;
                    }
                    Log.e(TAG, "Couldn't open " + mName
                            + " for writing (will try read-only):", ex);
                    final String path = mContext.getDatabasePath(mName).getPath();
                    db = SQLiteDatabase.openDatabase(path, mFactory,
                            SQLiteDatabase.OPEN_READONLY, mErrorHandler);
                }
            }
            ........

　　其實是調用了mContext的getDataBasePath方法，這個方法是在ContextImpl中實現的，再看下源碼

@Override
    public File getDatabasePath(String name) {
        return validateFilePath(name, false);
    }

private File validateFilePath(String name, boolean createDirectory) {
        File dir;
        File f;

        if (name.charAt(0) == File.separatorChar) {
            String dirPath = name.substring(0, name.lastIndexOf(File.separatorChar));
            dir = new File(dirPath);
            name = name.substring(name.lastIndexOf(File.separatorChar));
            f = new File(dir, name);
        } else {
            dir = getDatabasesDir();
            f = makeFilename(dir, name);
        }

        if (createDirectory && !dir.isDirectory() && dir.mkdir()) {
            FileUtils.setPermissions(dir.getPath(),
                FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
                -1, -1);
        }

        return f;
    }

好吧，原來這么簡單，原來Android本身已經實現了自定義路徑的方法了，只要傳入的path的第一個字符為"/"就行了。

總結下就一句話，只要傳入自定義路徑的完整路徑就好了。。。。