在Android应用程序中从Sqlite数据库读取数据。

Question

我想从数据库中读取数据。我手动导入了数据库sqlite，现在只需要在android应用程序中进行连接，并希望读取行并将它们显示在文本字段中，但是我使用的代码是每次都使数据库变为新的或正在创建表中再次在该数据库中，我得到一个运行时错误。

我的代码是：

package com.example.dbexample; 

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

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

public class DatabaseHandler extends SQLiteOpenHelper { 

    // All Static variables 
    // Database Version 
    private static final int DATABASE_VERSION = 1; 

    // Database Name 
    private static final String DATABASE_NAME = "TranslatesManager"; 

    // Translates table name 
    private static final String TABLE_TRANSLATOR = "Words"; 

    // Translates Table Columns names 
    private static final String KEY_ID = "id"; 
    private static final String KEY_ENGLISHNAME = "Englishname"; 
    private static final String KEY_URDUNAME = "Urduname"; 

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

    // Creating Tables 
    @Override 
    public void onCreate(SQLiteDatabase db) { 
    /* String CREATE_TranslateS_TABLE = "CREATE TABLE " + TABLE_TRANSLATOR + "(" 
       + KEY_ID + " INTEGER PRIMARY KEY," + KEY_ENGLISHNAME + " TEXT," 
       + KEY_URDUNAME + " TEXT" + ")"; 
     db.execSQL(CREATE_TranslateS_TABLE); 
    */ 
    } 

    // Upgrading database 
    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     // Drop older table if existed 
     // db.execSQL("DROP TABLE IF EXISTS " + TABLE_TRANSLATOR); 
     // Create tables again 
     //onCreate(db); 
    } 

// Adding new Translate 
    void addTranslate(Translate Translate) { 
     SQLiteDatabase db = this.getWritableDatabase(); 

     ContentValues values = new ContentValues(); 
     values.put(KEY_ENGLISHNAME, Translate.getName()); // Translate Name 
     values.put(KEY_URDUNAME, Translate.getUrduName()); // Translate Phone 

     // Inserting Row 
     db.insert(TABLE_TRANSLATOR, null, values); 
     db.close(); // Closing database connection 
    } 

    // Getting single Translate 
    Translate getTranslate(int id) { 
     SQLiteDatabase db = this.getReadableDatabase(); 

     Cursor cursor = db.query(TABLE_TRANSLATOR, new String[] { KEY_ID, 
       KEY_ENGLISHNAME, KEY_URDUNAME }, KEY_ID + "=?", 
       new String[] { String.valueOf(id) }, null, null, null, null); 
     if (cursor != null) 
      cursor.moveToFirst(); 

     Translate Translate = new Translate(Integer.parseInt 
       (cursor.getString(0)),cursor.getString(1), cursor.getString(2)); 
     // return Translate 
     return Translate; 
    } 

    // Getting All Translates 
    public List<Translate> getAllTranslates() { 
     List<Translate> TranslateList = new ArrayList<Translate>(); 
     // Select All Query 
     String selectQuery = "SELECT * FROM " + TABLE_TRANSLATOR; 

     SQLiteDatabase db = this.getWritableDatabase(); 
     Cursor cursor = db.rawQuery(selectQuery, null); 

     // looping through all rows and adding to list 
     if (cursor.moveToFirst()) { 
      do { 
       Translate Translate = new Translate(); 
       Translate.setID(Integer.parseInt(cursor.getString(0))); 
       Translate.setName(cursor.getString(1)); 
       Translate.setUrduName(cursor.getString(2)); 
       // Adding Translate to list 
       TranslateList.add(Translate); 
      } while (cursor.moveToNext()); 
     } 

     // return Translate list 
     return TranslateList; 
    } 

    // Updating single Translate 
    public int updateTranslate(Translate Translate) { 
     SQLiteDatabase db = this.getWritableDatabase(); 

     ContentValues values = new ContentValues(); 
     values.put(KEY_ENGLISHNAME, Translate.getName()); 
     values.put(KEY_URDUNAME, Translate.getUrduName()); 

     // updating row 
     return db.update(TABLE_TRANSLATOR, values, KEY_ID + " = ?", 
       new String[] { String.valueOf(Translate.getID()) }); 
    } 

    // Deleting single Translate 
    public void deleteTranslate(Translate Translate) { 
     SQLiteDatabase db = this.getWritableDatabase(); 
     db.delete(TABLE_TRANSLATOR, KEY_ID + " = ?", 
       new String[] { String.valueOf(Translate.getID()) }); 
     db.close(); 
    } 

    // Getting Translates Count 
    public int getTranslatesCount() { 
     String countQuery = "SELECT * FROM " + TABLE_TRANSLATOR; 
     SQLiteDatabase db = this.getReadableDatabase(); 
     Cursor cursor = db.rawQuery(countQuery, null); 
     cursor.close(); 

     // return count 
     return cursor.getCount(); 
    } 
    } 

翻译是类。 它只是id，englishname，urduname字段。

请更正此文件或找到错误，这样我才能知道如何从sqlLiteDatabase中读取文本框。

我的主要活动代码：

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main_db); 
    DatabaseHandler db = new DatabaseHandler(this);    
     // Inserting Translates 
      /// Log.d("Insert: ", "Inserting .."); 
    //db.addTranslate(new Translate("Ravi", "9100000000")); 
    //db.addTranslate(new Translate("Srinivas", "9199999999")); 
    //db.addTranslate(new Translate("Tommy", "9522222222")); 
    //db.addTranslate(new Translate("Karthik", "9533333333")); 

    // Reading all Translates 
    Log.d("Reading: ", "Reading all Translates.."); 
    List<Translate> Translates = db.getAllTranslates();  

    for (Translate cn : Translates) { 
     String log = "Id: "+cn.getID()+" ,Name: " + cn.getName() + 
                " ,Phone: " + cn.getUrduName(); 
      // Writing Translates to log 
    Log.d("Name: ", log); 
    } 
    TextView t1 = (TextView) findViewById(R.id.textView1); 
    TextView t2 = (TextView) findViewById(R.id.textView4); 
    TextView t3 = (TextView) findViewById(R.id.textView3); 

    for (Translate cn : Translates) 
    { 
     t1.setText(Integer.toString(cn.getID())); 
     t2.setText(cn.getName()); 
     t3.setText(cn.getUrduName()); 
    } 

} 

让我知道问题出在哪里，请。

Answer 1

如果要导入数据库，那么为什么要扩展用于创建数据库的SQLliteopenhelper类。 要使用现有的数据，您需要使用android中提供的其他类。以下链接可能对您有所帮助 http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html#http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html