在 android 应用程序中从 Sqlite 数据库读取数据。

Question

我正在尝试从数据库中读取数据。 我手动在sqlite导入了数据库，现在只想要在 android 应用程序中建立连接并想要读取行并将它们显示在文本字段中，但是我使用的代码要么每次都使数据库成为新的，要么正在创建该数据库中的表再次出现运行时错误。

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();
    }
    }

翻译是班级。 它只有 id、englishname、urduname 字段。

请更正此文件或查找错误，以便我知道如何从sqlLiteDatabase读取到文本框。

我的主要活动代码是：

    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());
    }

}

请让我知道问题出在哪里。

Answer 1

如果您要导入数据库，那么为什么要扩展用于创建数据库的 SQLliteopenhelper 类。 要使用现有数据，您需要使用 android 中提供的其他类.. 请参阅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