Android开发—数据库应用—访问数据表（SQLite OpenHelper） —添加查询

/* (程序头部注释开始)
* 程序的版权和版本声明部分
* Copyright (c) 2011, 烟台大学计算机学院学生
* All rights reserved.
* 文件名称：数据库应用—添加查询

* 作 者： 雷恒鑫
* 完成日期： 2012 年 08 月 14 日
* 版 本 号： V1.0
* 对任务及求解方法的描述部分
* 输入描述：
* 问题描述：
* 程序输出：

* 程序头部的注释结束

*/

 

方法：在“NotesDbAdapter”类中新增一个“getall”方法来查询“notes”数据表中的所有数据，修改后的“DummyNote.java”文件如下：

package com.demo.android.dummynote;import android.app.ListActivity;import android.database.Cursor;import android.os.Bundle;import android.widget.ArrayAdapter;import android.widget.ListAdapter;import android.widget.SimpleCursorAdapter;import android.content.Intent;import android.widget.ListView;public class DummyNote extends ListActivity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        //Tell the list view which view to display when the list is empty        getListView().setEmptyView(findViewById(R.id.empty));        setAdapter();    }    private String[] note_array = {    "gasolin",    "crota",    "louk",    "magicion"    };     private NotesDbAdapter mDbHelper;    private Cursor mNotesCursor;    private void setAdapter(){    mDbHelper = new NotesDbAdapter(this);    mDbHelper.open();    fillData();    }    private void fillData(){    mNotesCursor = mDbHelper.getall();    startManagingCursor(mNotesCursor);        //Create an array to specify the field we want to display in the list    String[] from = new String[]{NotesDbAdapter.KEY_NOTE};        //an array of the fields we want to bind those fields to    int[] to = new int[]{android.R.id.text1};        //Now create a simple cursor adapter    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,    android.R.layout.simple_list_item_1,mNotesCursor,from,to);    setListAdapter(adapter);    }}

修改后的“DummyDbAdapter.java”文件如下：

 

package com.demo.android.dummynote;import android.content.Context;import android.database.Cursor;import android.database.SQLException;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.database.sqlite.SQLiteDatabase.CursorFactory;public class NotesDbAdapter {private static final String DATABASE_NAME = "notes.db";private static final int DATABASE_VERSION = 1;private static final String DATABASE_TABLE = "notes";private static final String DATABASE_CREATE = "creat table notes("+ "_id INTEGER PRIMARY KEY," + "note TEXT," + "created INTEGER,"+ "modified INTEGER" + ");";private static class DatabaseHelper extends SQLiteOpenHelper {public DatabaseHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);// TODO Auto-generated constructor stub}@Overridepublic void onCreate(SQLiteDatabase db) {// TODO Auto-generated method stubdb.execSQL(DATABASE_CREATE);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stubdb.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);onCreate(db);}}private Context mCtx = null;private DatabaseHelper dbHelper;private SQLiteDatabase db;public NotesDbAdapter(Context ctx) {this.mCtx = ctx;}public NotesDbAdapter open() throws SQLException {dbHelper = new DatabaseHelper(mCtx);db = dbHelper.getWritableDatabase();return this;}public void close() {dbHelper.close();}private static final String KEY_ROWID = "_id";static final String KEY_NOTE = "note";private static final String KEY_CREATED = "created";// get all entriespublic Cursor getall() {return db.rawQuery("SELECT * FROM notes", null);}}

 

经验积累：

1.我学会了如何使用“mDbHelper.getall()”语句。

2.“ListActivity”提供的“setListAdapter”方法，是将接口绑定到“ListView”界面组件上。