Question

在我的测试Android应用程序中，我打算创建并访问数据库文件，该文件将位于SD卡上。我在一个类的帮助下使用main活动，该类扩展了SQLiteOpenHelper。我想以与以前相同的方式使用它，但我必须以某种方式更改数据库PATH。你知道吗，如何实现它？

THX

我当前扩展SQLiteOpenHelper的类的代码：

public class DatabaseDefinition extends SQLiteOpenHelper{
private static final String DATABASE_NAME="test.db";
private static final int DATABASE_VERSION=1;

public DatabaseDefinition(Context context) {
    super(context,DATABASE_NAME,null, DATABASE_VERSION);

}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE "+TABLE_NAME+" ("+ _ID +" INTEGER PRIMARY KEY AUTOINCREMENT, "+ NAME+" TEXT NOT NULL, " +SURNAME+" TEXT NOT NULL, "+PHONE+" INT NOT NULL);");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME);
    onCreate(db);

}

我的主要代码：

public class DatabaseExampleActivity extends Activity {
   private DatabaseDefinition database;
   private static String[] FROM={_ID, NAME, SURNAME,PHONE};
   private static String ORDER_BY=" DESC";


   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       database= new DatabaseDefinition(this); 
       try{
         String name = null;
         String surname=null;
         int phone=0;
         addEvent("John", "Black", 111012345);

    }finally{
        database.close();
    }
  }



}

Answer 1

首先，您必须指定SD卡的路径。您可以通过创建如下字符串来实现：

public static final String  DATABASE_FILE_PATH = "/sdcard";

但你应该致电

Environment.getExternalStorageDirectory()

获取SD卡的根路径并使用它创建数据库。之后，您可以根据需要创建数据库。这是一个例子

public class DatabaseHelper
{ 
   private static final String TAG                  = "DatabaseHelper";

  public static final String  DATABASE_FILE_PATH      = Environment.getExternalStorageDirectory();
  public static final String  DATABASE_NAME      = "mydb"; 
  public static final String  TRACKS_TABLE        = "tracks";
  public static final String  TRACK_INFO_TABLE        = "track_info";

  private static final String TRACKS_TABLE_CREATE     = "create table "
           + TRACKS_TABLE
           + " (_id integer primary key autoincrement, title text not null, description text null, created_at date not null);";

  private static final String TRACK_INFO_TABLE_CREATE = "create table " 
           + TRACK_INFO_TABLE 
           + " (_id integer primary key autoincrement, track_id integer not null, latitude real not null, longitude real not null, altitude real not null, created_at date not null);";

private SQLiteDatabase      database;

public DatabaseHelper() 
{  
    try
    {
        database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,SQLiteDatabase.OPEN_READWRITE);
    }
    catch (SQLiteException ex)
    {
        Log.e(TAG, "error -- " + ex.getMessage(), ex);
        // error means tables does not exits
        createTables();
    }
    finally
    {
        DBUtil.safeCloseDataBase(database);
    }
}

private void createTables()
{
    database.execSQL(TRACKS_TABLE_CREATE);
    database.execSQL(TRACK_INFO_TABLE_CREATE);
}

public void close()
{
    DBUtil.safeCloseDataBase(database);
}

public SQLiteDatabase getReadableDatabase()
{
    database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,
            SQLiteDatabase.OPEN_READONLY);
    return database;
}

public SQLiteDatabase getWritableDatabase()
{
    database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,
            SQLiteDatabase.OPEN_READWRITE);
    return database;
}

最后，您必须在清单中设置权限，如下所示：android.permission.WRITE_EXTERNAL_STORAGE

祝你好运:) Arkde

Answer 2

如果你们有些人想在sd卡上创建sqlite数据库，但你还是想要继续使用扩展sqliteOpenHelper的类，您可以访问this answer。

您只需添加另一个类，在您的类（扩展sqliteOpenHelper）中在super（）中实现它，然后更改新类的路径。

注意：如果您使用的是HC或ICS，则需要在路径中描述“external_sd”。因为HC和ICS仍会报告物理内置到设备中的存储

SQLiteOpenHelper - 在SD卡上创建数据库

2 个答案: