Question

需要使用现有的Database Sqlite（我在Assets文件夹中添加），但不知道如何处理，我没有看到任何可以帮助我的完整示例。

如果有人知道任何好的例子或者可以提供帮助，我将非常感激。

Ps：我是Android新手！

谢谢

Answer 1

创建一个活动说SQLDemo.java

   package org.example.sqldemo;

import static android.provider.BaseColumns._ID;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;

public class SQLDemo extends Activity {
  EventDataSQLHelper eventsData;
  TextView output;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    output = (TextView) findViewById(R.id.output);

    eventsData = new EventDataSQLHelper(this);
    addEvent("Hello Android Event");
    Cursor cursor = getEvents();
    showEvents(cursor);
  }

  @Override
  public void onDestroy() {
    eventsData.close();
  }

  private void addEvent(String title) {
    SQLiteDatabase db = eventsData.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(EventDataSQLHelper.TIME, System.currentTimeMillis());
    values.put(EventDataSQLHelper.TITLE, title);
    db.insert(EventDataSQLHelper.TABLE, null, values);

  }

  private Cursor getEvents() {
    SQLiteDatabase db = eventsData.getReadableDatabase();
    Cursor cursor = db.query(EventDataSQLHelper.TABLE, null, null, null, null,
        null, null);

    startManagingCursor(cursor);
    return cursor;
  }

  private void showEvents(Cursor cursor) {
    StringBuilder ret = new StringBuilder("Saved Events:\n\n");
    while (cursor.moveToNext()) {
      long id = cursor.getLong(0);
      long time = cursor.getLong(1);
      String title = cursor.getString(2);
      ret.append(id + ": " + time + ": " + title + "\n");
    }
    output.setText(ret);
  }
}

现在按名称EventDataSQLHelper.java

创建数据库助手.java类

   package org.example.sqldemo;

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

/** Helper to the database, manages versions and creation */
public class EventDataSQLHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "events.db";
    private static final int DATABASE_VERSION = 1;

    // Table name
    public static final String TABLE = "events";

    // Columns
    public static final String TIME = "time";
    public static final String TITLE = "title";

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

// if you keep the DATABASE_NAME as null, application will treat the DB as in memory DB which means application destroys the DB on exit
        }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "create table " + TABLE + "( " + BaseColumns._ID
                + " integer primary key autoincrement, " + TIME + " integer, "
                + TITLE + " text not null);";
        Log.d("EventsData", "onCreate: " + sql);
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (oldVersion >= newVersion)
            return;

        String sql = null;
        if (oldVersion == 1) 
            sql = "alter table " + TABLE + " add note text;";
        if (oldVersion == 2)
            sql = "";

        Log.d("EventsData", "onUpgrade  : " + sql);
        if (sql != null)
            db.execSQL(sql);
    }

}

我希望这对你有用：）

Answer 2

尝试使用此代码将现有数据库从Asset文件夹复制到Android inmemory

private void copyDataBase() throws IOException{

    //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

    //Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);

    //transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer))>0){
        myOutput.write(buffer, 0, length);
    }

    //Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();

}

Answer 3

这里有一个很好的例子：

http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

要记住的最重要的部分是本教程的第1部分，您将不得不使用一些Android元数据稍微修改数据库，以便与框架SQLite类顺利集成。

希望有帮助！

需要使用数据库但不知道如何在Android中执行此操作

3 个答案: