在android的Sqlite数据库中执行查询

我已经使用Sqlitebrowser手动创建了一个数据库，其中包含一个Table1表，该表有5列CellID、Latitude、Longitude、Address和city。然后我使用以下类访问数据库：

package com.example.sampledbapp;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

    public class DatabaseHelper extends SQLiteOpenHelper{

    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.example.sampledbapp/databases/";

    private static String DB_NAME = "sampleDb.db";

    private SQLiteDatabase myDataBase;

    private final Context myContext;

    /**
      * Constructor
      * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
      * @param context
      */
    public DatabaseHelper(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;
    }   

    /**
      * Creates a empty database on the system and rewrites it with your own database.
      * */
    public void createDataBase() throws IOException{

    boolean dbExist = checkDataBase();

    if(dbExist){
    //do nothing - database already exist
    }else{

    //By calling this method and empty database will be created into the default system path
    //of your application so we are gonna be able to overwrite that database with our database.
    this.getReadableDatabase();

    try {

    copyDataBase();

    } catch (IOException e) {

    throw new Error("Error copying database");

    }
    }

    }

    /**
      * Check if the database already exist to avoid re-copying the file each time you open the application.
      * @return true if it exists, false if it doesn't
      */
    private boolean checkDataBase(){

    SQLiteDatabase checkDB = null;

    try{
    String myPath = DB_PATH + DB_NAME;
    checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }catch(SQLiteException e){

    //database does't exist yet.

    }

    if(checkDB != null){

    checkDB.close();

    }

    return checkDB != null ? true : false;
    }

    /**
      * Copies your database from your local assets-folder to the just created empty database in the
      * system folder, from where it can be accessed and handled.
      * This is done by transfering bytestream.
      * */
    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();

    }

    public void openDataBase() throws SQLException{

    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }

    @Override
    public synchronized void close() {

    if(myDataBase != null)
    myDataBase.close();

    super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    // Add your public helper methods to access and get content from the database.
    // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
    // to you to create adapters for your views.

    }

我有一个名为find的按钮，在该按钮上执行以下代码：

public void btn_Click(View arg){
     DatabaseHelper myDbHelper;
     myDbHelper = new DatabaseHelper(this);

     try {

     myDbHelper.createDataBase();

     } catch (IOException ioe) {

     throw new Error("Unable to create database");

     }

     try {

     myDbHelper.openDataBase();

     SQLiteDatabase db = myDbHelper.getReadableDatabase();
     String selectQuery = "select CellID from Table1 where _id='2'";
     Cursor cursor = db.rawQuery(selectQuery, null);
     cursor.close();
      Toast.makeText(getApplicationContext(), ""+cursor.getInt(0), Toast.LENGTH_LONG).show();
     }catch(SQLException sqle){

     throw sqle;

     }
}

我得到以下错误：

01-15 17:23:09.834: E/AndroidRuntime(2372): Caused by: android.database.sqlite.SQLiteException: no such table: Table1 (code 1): , while compiling: select CellID from Table1 where _id='2'
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
01-15 17:23:09.834: E/AndroidRuntime(2372):     at com.example.sampledbapp.MainActivity.btn_Click(MainActivity.java:49)
01-15 17:23:09.834: E/AndroidRuntime(2372):     ... 14 more

---

请帮忙

因此，我将告诉您，您需要的代码如下所示：

public class DatabaseHelper extends SQLiteOpenHelper{

private static String DB_NAME = "sampleDb.db";

private SQLiteDatabase myDataBase;

private final Context myContext;

/**
  * Constructor
  * Takes and keeps a reference of the passed context in order to access to the application    assets and resources.
  * @param context
  */
public DatabaseHelper(Context context) {

super(context, DB_NAME, null, 1);
myDatabase = getWritableDatabase();  <-- important part
this.myContext = context;
}   

@Override
public synchronized void close() {

if(myDataBase != null)
myDataBase.close();

super.close();

}

@Override
public void onCreate(SQLiteDatabase db) {
    put in here your Sql to generate your tables inside the database will be called if no
    database exists yet on the device
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
     this method doesn't needs to be implemented yet
}

 public void yourSelectQuery(){
 String selectQuery = "select CellID from Table1 where _id=2";
 Cursor cursor = db.rawQuery(selectQuery, null);
 cursor.moveToFirst();
  Toast.makeText(getApplicationContext(), ""+cursor.getInt(0), Toast.LENGTH_LONG).show();
 cursor.close();
}  

---

ofc您不应该在数据库处理程序类之外干杯。我认为您不理解这个问题。我不想从我的程序中生成表，正如您所提到的：public void onCreateSQLiteDatabase db{如果设备上还没有数据库，将调用您在数据库中生成表的Sql}我想对已经创建的sqlite数据库执行查询。请帮助我。这也适用于执行querys->look in method yourSelectQuerybtw您还应该考虑您已经生成的数据库，因为该表确实丢失：没有这样的表：表1代码1:，

public void btn_Click(View arg){
     DatabaseHelper myDbHelper;
     myDbHelper = new DatabaseHelper(this);
     myDbHelper.yourSelectQuery();
}