如何進行Android數據庫操作

強烈建議，在自己android數據庫接收或發出一個系統action的時候，要名副其實。比如你響應一個vIEw動作，做的確實edit的勾當，你發送一個pick消息，其實你想讓別人做edit的事，這樣都會造成混亂。

一個好的習慣是創建一個輔助類來簡化你的android數據庫交互。考慮創建一個數據庫適配器，來添加一個與數據庫交互的包裝層。它應該提供直觀的、強類型的方法，如添加、刪除和更新項目。數據庫適配器還應該處理查詢和對創建、打開和關閉數據庫的包裝。

它還常用靜態的android數據庫常量來定義表的名字、列的名字和列的索引。下面的代碼片段顯示了一個標准數據庫適配器類的框架。它包括一個SQLiteOpenHelper類的擴展類，用於簡化打開、創建和更新數據庫。

import android.content.Context;  
 
import android.database.*;  
 
import android.database.sqlite.*;  
 
import android.database.sqlite.SQLiteDatabase.CursorFactory;  
 
import android.util.Log;  
 
public class MyDBAdapter   
 
{  // The name and column index of each column in your database.  
 
public static final String KEY_NAME=”name”;  
 
public static final int NAME_COLUMN = 1;  
 
   
 
// TODO: Create public fIEld for each column in your table.  
 
// SQL Statement to create a new database.  
 
private static final String DATABASE_CREATE = “create table “ +  
 
DATABASE_TABLE + “ (“ + KEY_ID + “ integer primary key autoincrement, “ +  
 
KEY_NAME + “ text not null);”;  
 
   
 
// Variable to hold the database instance  
 
private SQLiteDatabase db;  
 
   
 
// Context of the application using the database.  
 
private final Context context;  
 
   
 
// Database open/upgrade helper  
 
private myDbHelper dbHelper;  
 
   
 
public MyDBAdapter(Context _context) {  
 
context = _context;  
 
dbHelper = new myDbHelper(context, DATABASE_NAME, null, DATABASE_VERSION);  
 
}  
 
   
 
public MyDBAdapter open() throws SQLException {  
 
db = dbHelper.getWritableDatabase();  
 
return this;  
 
}  
 
   
 
public void close() {  
 
db.close();  
 
}  
 
   
 
public long insertEntry(MyObject _myObject) {  
 
ContentValues contentValues = new ContentValues();  
 
// TODO fill in ContentValues to represent the new row  
 
return db.insert(DATABASE_TABLE, null, contentValues);  
 
}  
 
   
 
public boolean removeEntry(long _rowIndex) {  
 
return db.delete(DATABASE_TABLE, KEY_ID + “=” + _rowIndex, null) > 0;  
 
}  
 
public Cursor getAllEntrIEs () {  
 
return db.query(DATABASE_TABLE, new String[] {KEY_ID, KEY_NAME},  
 
null, null, null, null, null);  
 
}  
 
public MyObject getEntry(long _rowIndex) {  
 
MyObject objectInstance = new MyObject();  
 
// TODO Return a cursor to a row from the database and  
 
// use the values to populate an instance of MyObject  
 
return objectInstance;  
 
}  
 
public int updateEntry(long _rowIndex, MyObject _myObject) {  
 
String where = KEY_ID + “=” + _rowIndex;  
 
ContentValues contentValues = new ContentValues();  
 
// TODO fill in the ContentValue based on the new object  
 
return db.update(DATABASE_TABLE, contentValues, where, null);  
 
}  
 
   
 
private static class myDbHelper extends SQLiteOpenHelper   
 
{  
 
public myDbHelper(Context context, String name, CursorFactory factory, int version) {  
 
super(context, name, factory, version);  
 
}  
 
   
 
// Called when no database exists in  
 
// disk and the helper class needs  
 
// to create a new one.  
 
@Override  
 
public void onCreate(SQLiteDatabase _db) {  
 
_db.execSQL(DATABASE_CREATE);  
 
}