Question

对于我的实习，我正在开发一个Android应用程序，并试图让一个本地数据库运行以设置离线referal，以及每次用户返回某个活动时阻止新的BasicAuth请求和所需的数据库拉取。为了达到这个目的，我正在尝试建立一个SQLite数据库，但事情并没有真正解决。

我目前正在使用this教程来尝试设置数据库。对于我的应用程序，我专门编辑了MySQLiteHelper和TicketsDataSource类。

MySQLiteHelper：

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

public class MySQLiteHelper extends SQLiteOpenHelper {

public static final String TABLE_TICKETS = "tickets";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_TICKET_ID = "ticketId";
public static final String COLUMN_TICKET_TITLE = "ticketTitle";
public static final String COLUMN_PROJECT_NAME = "projectName";
public static final String COLUMN_CLIENT_NAME = "clientName";
public static final String COLUMN_TICKET_DESCRIPTION = "ticketDescription";

private static final String DATABASE_NAME = "commments.db";
private static final int DATABASE_VERSION = 1;

// Database creation SQL statement
private static final String DATABASE_CREATE = "create table "
      + TABLE_TICKETS 
      + "(" 
      + COLUMN_ID + " integer primary key autoincrement, " 
      + COLUMN_TICKET_ID + " text not null, " 
      + COLUMN_TICKET_TITLE+ " text not null, " 
      + COLUMN_PROJECT_NAME+ " text not null, " 
      + COLUMN_CLIENT_NAME+ " text not null, " 
      + COLUMN_TICKET_DESCRIPTION+ " text not null);";

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

@Override
public void onCreate(SQLiteDatabase database) {
  database.execSQL(DATABASE_CREATE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  Log.w(MySQLiteHelper.class.getName(),
    "Upgrading database from version " + oldVersion + " to "
        + newVersion + ", which will destroy all old data");
  db.execSQL("DROP TABLE IF EXISTS " + TABLE_TICKETS);
  onCreate(db);
}
}

TicketsDataSource：

import java.util.ArrayList;
import java.util.List;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;

public class TicketsDataSource {

  // Database fields
  private SQLiteDatabase database;
  private MySQLiteHelper dbHelper;
  private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
      MySQLiteHelper.COLUMN_TICKET_ID, MySQLiteHelper.COLUMN_TICKET_TITLE, MySQLiteHelper.COLUMN_PROJECT_NAME,
      MySQLiteHelper.COLUMN_CLIENT_NAME, MySQLiteHelper.COLUMN_TICKET_DESCRIPTION};

  public TicketsDataSource(Context context) {
    dbHelper = new MySQLiteHelper(context);
  }

  public void open() throws SQLException {
    database = dbHelper.getWritableDatabase();
  }

  public void close() {
    dbHelper.close();
  }

  public Ticket createTicket(String ticket) {
    ContentValues values = new ContentValues();
    values.put(MySQLiteHelper.COLUMN_TICKET_DESCRIPTION, ticket);
    long insertId = database.insert(MySQLiteHelper.TABLE_TICKETS, null,
    values);
    Cursor cursor = database.query(MySQLiteHelper.TABLE_TICKETS,
    allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
    null, null, null);
    cursor.moveToFirst();
    Ticket newTicket = cursorToTicket(cursor);
    cursor.close();
    return newTicket;
  }

  public void deleteTicket(Ticket ticket) {
    long id = ticket.getId();
    System.out.println("Ticket deleted with id: " + id);
    database.delete(MySQLiteHelper.TABLE_TICKETS, MySQLiteHelper.COLUMN_ID
        + " = " + id, null);
  }

  public List<Ticket> getAllTickets() {
    List<Ticket> tickets = new ArrayList<Ticket>();

    Cursor cursor = database.query(MySQLiteHelper.TABLE_TICKETS,
        allColumns, null, null, null, null, null);

    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
      Ticket ticket = cursorToTicket(cursor);
      tickets.add(ticket);
      cursor.moveToNext();
    }
    // make sure to close the cursor
    cursor.close();
    return tickets;
  }

  private Ticket cursorToTicket(Cursor cursor) {
    Ticket ticket = new Ticket();
    ticket.setId(cursor.getLong(0));
    ticket.setTicketId(cursor.getLong(1));
    ticket.setTicketTitle(cursor.getString(2));
    ticket.setClientName(cursor.getString(3));
    ticket.setProjectName(cursor.getString(4));
    ticket.setTicketDescription(cursor.getString(5));
    return ticket;
  }
}

在我的活动中，我首先通过定义它来调用TicketsDataSource类：

private TicketsDataSource datasource;

然后从if语句中调用它，检查服务器是否已成功调用：

else {
 datasource = new TicketsDataSource(this);
 datasource.open();
}

不幸的是，当我切换到DDMS视图时，在多次运行应用程序后，我看不到任何正在创建的数据库。事实上，我甚至无法在DDMS视图的主“data”文件夹中看到任何其他文件夹。我没有得到任何错误消息（除了'eglSurfaceAttrib未实现'，这在谷歌搜索后似乎无关紧要），但是当我在MySQLiteHelper类的onCreate函数中放置系统打印时，它不会在日志中打印任何内容（它确实出现在else语句中）。我不确定我的Java代码是否有问题，或者我的常规设置是否有问题。

先谢谢你的帮助，丹尼斯

Answer 1

如果您是，您将只能看到/ data文件夹中的文件/文件夹 a：使用模拟器，或 b：使用root电话。这些是受保护的文件夹，不能被凡人看到。

对你所写的内容的真正考验是这样的 - 你能写入数据库并从数据库中读取吗？

Answer 2

对我来说最好的android数据库故障排除解决方案是将此方法添加到我的SQliteHelper类中，该类将sqlite数据库复制到您测试的设备上的SD卡。然后，您可以使用任意数量的sqlite manager桌面应用程序打开它，并验证您的表和数据。您不需要以这种方式root手机。在开发过程中，我坚持调用这个方法，我需要获取db的快照：

 public static void backup() {
        try {
            File sd = Environment.getExternalStorageDirectory();
            File data = Environment.getDataDirectory();

            if (sd.canWrite()) {
                String currentDBPath = "//data//com.example//databases//" + DATABASE_NAME;
                String backupDBPath = DATABASE_VERSION + DATABASE_NAME;
                File currentDB = new File(data, currentDBPath);
                File backupDB = new File(sd, "//Download//" + backupDBPath);

                if (currentDB.exists()) {
                    FileChannel src = new FileInputStream(currentDB).getChannel();
                    FileChannel dst = new FileOutputStream(backupDB).getChannel();
                    dst.transferFrom(src, 0, src.size());
                    src.close();
                    dst.close();
                }
            }
        } catch (Exception e) {
            Log.e(TAG, e.getMessage());
        }
    }

您需要为清单添加外部存储权限。

Android SQLite数据库，创建数据库和DDMS透视图

2 个答案: