查詢不起作用數據庫android

Question

我正在用SQL開發一個簡單的Android應用程序。我遵循以下指南 - Using your own SQLite database in Android applications

當試圖執行查詢數據庫時出現錯誤。

這裏是我的DataBaseHelp.Java類：

package namae.nombebe; 

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/namae.nombebe/databases/"; 

    private static String DB_NAME = "myDBName"; 

    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. 

} 

這也是我打開我的數據庫的方式：

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

     DataBaseHelper myDbHelper = new DataBaseHelper(this); 

     try 
     { 
       myDbHelper.createDataBase(); 
     } 
     catch (IOException ioe) 
     { 
      throw new Error("Unable to create database"); 
     } 

     try 
     { 
      myDbHelper.openDataBase(); 
     } 
     catch(SQLException sqle) 
     { 
      throw sqle; 
     } 

     myDataBase = myDbHelper.getWritableDatabase(); 

     Cursor c = myDataBase.rawQuery("SELECT * FROM Astuces", null); 
// problem on this query 
    } 

所以查詢不起作用。 （如果我不把它的應用程序工作）

我有一個表Astuces。

錯誤：

07-30 10:56:53.869: E/AndroidRuntime(503): java.lang.RuntimeException: Unable to start activity ComponentInfo{namae.nombebe/namae.nombebe.NomBebeActivity}: android.database.sqlite.SQLiteException: no such table: Astuces: , while compiling: SELECT * FROM Astuces 

我們可以看到，我說有沒有表Astuces我真的有它，所以我不明白爲什麼我可以找到它。

Answer 1

我幾個星期前跟着同一個鏈接。在開始使用代碼之前，您必須考慮一些重要的事情：

1 - 您需要爲您的SQLite file調用android_metadata添加一個表格，然後將en_US插入它。

2 - 您必須將id重命名爲_id。

3 - 您應該將您的SQLite文件複製到項目的assets文件夾中。

然後您可以使用代碼。你如何完成這3個步驟？

myDataBase class哪裏？你在你的代碼中實現了哪些方法？

myDataBase = myDbHelper.getWritableDatabase(); 
Cursor c = myDataBase.rawQuery("SELECT * FROM Astuces", null); 

您可能需要有這樣的事情在你的DataBaseHelper類

public Cursor fetchAllEntries() { 
      //includes all column names 
     String[] projection = new String[] { KEY_ROWID, USER_ID, START, END }; 
     String restrict = null; // Get all entries 
      String orderby = null; 
     return myDataBase.query(TABLE_NAME, projection, restrict, null, null, null, orderby); 
    } 

，並在主要活動稱呼它：

Cursor entryCursor = db.fetchAllEntries();