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我在资产中导入了一个试用数据库，它已预先填充。它有 6 列：_ID、QUESTION、ANSWER、OPTION1、OPTION2、OPTION3，我现在有 10 行。我正在做一些类似测验的事情。我想要的是当我打开测验活动以读取一个随机行，然后将 setText 设置为我创建的 4 个按钮，button1=ANSWER，button2=OPTION1，button3=OPTION2，button=OPTION3，再次随机。我知道如何将文本设置为按钮等等，我只想知道如何从数据库中读取所有内容。我有导入数据库的 DataBaseHelper 类：

package rs.androidaplikacijekvizopstekulture;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import rs.androidaplikacijekvizopstekulture.Pitanja;

public class DataBaseHelper extends SQLiteOpenHelper
{
private static String TAG = "DataBaseHelper"; // Tag just for the LogCat window
//destination path (location) of our database on device
private static String DB_PATH = ""; 
private static String DB_NAME ="pitanja";// Database name
private static final int DATABASE_VERSION = 1;
private static SQLiteDatabase mDataBase; 
private final Context mContext;
private static final String KEY_ID = "_ID";
private static final String KEY_PITANJE = "PITANJE";
private static final String KEY_ODGOVOR = "ODGOVOR";
private static final String KEY_OPCIJA1 = "OPCIJA1";
private static final String KEY_OPCIJA2 = "OPCIJA2";
private static final String KEY_OPCIJA3 = "OPCIJA3";
private static final String TABLE_NAME = "tblPitanja";

public DataBaseHelper(Context mojContext) 
{
    super(mojContext, DB_NAME, null, 1);// 1? its Database Version
    DB_PATH = mojContext.getApplicationInfo().dataDir + "/databases/";
    this.mContext = mojContext;
}

public void createDataBase() throws IOException
{
    //If database not exists copy it from the assets

    boolean mDataBaseExist = checkDataBase();
    if(!mDataBaseExist)
    {
        this.getReadableDatabase();
        this.close();
        try 
        {
            //Copy the database from assests
            copyDataBase();
            Log.e(TAG, "createDatabase database created");
        } 
        catch (IOException mIOException) 
        {
            throw new Error("ErrorCopyingDataBase");
        }
    }
}
    //Check that the database exists here: /data/data/your package/databases/Da Name
    private boolean checkDataBase()
    {
        File dbFile = new File(DB_PATH + DB_NAME);
        //Log.v("dbFile", dbFile + "   "+ dbFile.exists());
        return dbFile.exists();
    }

    //Copy the database from assets
    private void copyDataBase() throws IOException
    {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer))>0)
        {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    //Open the database, so we can query it
    public boolean openDataBase() throws SQLException
    {
        String mPath = DB_PATH + DB_NAME;
        //Log.v("mPath", mPath);
        mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
        //mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
        return mDataBase != null;
    }

    @Override
    public synchronized void close() 
    {
        if(mDataBase != null)
            mDataBase.close();
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase arg0) {
        }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        Log.w("DataBaseHelper", "Upgrading database!!!!!");
          onCreate(arg0);

    }

}

在遵循在线教程之一之后，我还制作了一个 TestAdapter 类。我实际上不知道我是否需要这门课。

package rs.androidaplikacijekvizopstekulture;

import java.io.IOException;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

public class TestAdapter 
{
    protected static final String TAG = "DataAdapter";

    private final Context mContext;
    private SQLiteDatabase mDb;
    private DataBaseHelper mDbHelper;

    public TestAdapter(Context context) 
    {
        this.mContext = context;
        mDbHelper = new DataBaseHelper(mContext);
    }

    public TestAdapter createDatabase() throws SQLException 
    {
        try 
        {
            mDbHelper.createDataBase();
        } 
        catch (IOException mIOException) 
        {
            Log.e(TAG, mIOException.toString() + "  UnableToCreateDatabase");
            throw new Error("UnableToCreateDatabase");
        }
        return this;
    }

    public TestAdapter open() throws SQLException 
    {
        try 
        {
            mDbHelper.openDataBase();
            mDbHelper.close();
            mDb = mDbHelper.getReadableDatabase();
        } 
        catch (SQLException mSQLException) 
        {
            Log.e(TAG, "open >>"+ mSQLException.toString());
            throw mSQLException;
        }
        return this;
    }

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

     public Cursor getTestData()
     {
         try
         {
             String sql ="SELECT * FROM tblPitanja";

             Cursor mCur = mDb.rawQuery(sql, null);
             if (mCur!=null)
             {
                mCur.moveToNext();
             }
             return mCur;
         }
         catch (SQLException mSQLException) 
         {
             Log.e(TAG, "getTestData >>"+ mSQLException.toString());
             throw mSQLException;
         }
     }
}
4

1 回答 1

5

为此，您可以在 sql 函数 ex 中使用 RANDOM。

String sql = "select * from yourtable order BY RANDOM() LIMIT 1";

于 2013-02-27T15:04:24.537 回答