SQLite數據庫操作封裝

public class mydaHelper extends SQLiteOpenHelper{

//構造函數，這個是必須有的包括四個參數，分別是容器，數據庫的名字，CursorFactory暫時不用管，版本號
public mydaHelper(Context context, String name, CursorFactory factory,
   int version) {
  super(context, name, factory, version);
}
// 自己寫的一個含有三個參數的構造函數，它其實就是調用上面的構造函數
 public mydaHelper(Context context, String name,
   int version) {
  this(context, name, null, version);
}
//同樣這是自己寫的一個含有兩個參數的構造函數，來自于對上面的調用
 public mydaHelper(Context context, String name) {
  this(context, name,1);
}
//創建數據庫時調用，會建立一個表
 public void onCreate(SQLiteDatabase db) {
System.out.println("create database");
  db.execSQL("create table user(id int,name text)");
 }
//更新數據庫時被調用
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  System.out.println("update a Database");
}
}</pre>使用代碼: 
  
public class Activity01 extends Activity {
private Button button1;
private Button button2;
private Button button3;
private Button button4;
private Button button5;
private TextView textview;
private EditText  editText1;
private EditText editText2;


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


//實例化按鈕和文本以及編輯框
        textview = (TextView) this.findViewById(R.id.textView1);
        button1 = (Button) this.findViewById(R.id.button1);
        button1.setText("create");
        button2 =(Button) this.findViewById(R.id.button2);
        button2.setText("insert");
        button3 =(Button) this.findViewById(R.id.button3);
        button4 =(Button) this.findViewById(R.id.button4);
        button3.setText("更新");
        button4.setText("查詢");
        button5 = (Button) this.findViewById(R.id.button5);
        editText1 = (EditText) this.findViewById(R.id.editText1);
        editText2 = (EditText) this.findViewById(R.id.editText2);
        editText1.setText("");
        editText2.setText("");
        editText1.setEnabled(true);
        editText2.setEnabled(true);

    button1.setOnClickListener(new Button.OnClickListener(){
     public void onClick(View v){


//調用SQLiteOpenHelper構造函數
          mydaHelper dbh = new mydaHelper(Activity01.this,"my database");
//通過對mydaHelper的調用創建數據庫并來執行CreateTable方法創建一個user表
          SQLiteDatabase db = dbh.getReadableDatabase();
         }
        });
       button2.setOnClickListener(new Button.OnClickListener(){
        public void onClick(View v){
//通過ContentValues來向數據庫里寫數據
         ContentValues contentValues = new ContentValues();
         contentValues.put("id", editText1.getText().toString());
         contentValues.put("name", editText2.getText().toString());
         mydaHelper dbh = new mydaHelper(Activity01.this,"my database");
得到一個可寫入的數據庫
         SQLiteDatabase db = dbh.getWritableDatabase();
將數據寫入
         db.insert("user", null, contentValues);
        }
       });
       button3.setOnClickListener(new Button.OnClickListener(){
        public void onClick(View v){
         mydaHelper dbh= new mydaHelper(Activity01.this,"my database");
         ContentValues contentValues = new ContentValues();
         contentValues.put("name", editText2.getText().toString());
         SQLiteDatabase db= dbh.getWritableDatabase();
更新數據庫通過"id=?",new String[]{editText1.getText().toString()}確定要更新的位置
         db.update("user", contentValues, "id=?",new String[]{editText1.getText().toString()} );
        }
       });
       button4.setOnClickListener(new Button.OnClickListener(){
        public void onClick(View v){
         String n = "";
         mydaHelper dbh = new mydaHelper(Activity01.this,"my database");
         SQLiteDatabase db=  dbh.getReadableDatabase();
查詢數據庫幾個參數分別是數據庫的名字，要返回的內容，確定內容的標志比如id，標志內容，其他的不做介紹
         Cursor cursor = db.query("user", null, null,  null, null,null, null
           );
//通過指針的移動來確定是不是查詢完畢
         while(cursor.moveToNext()){
         得到內容
          int id = cursor.getInt(cursor.getColumnIndex("id"));
          String name = cursor.getString(cursor.getColumnIndex("name"));
          n += id+"  :  "+name+"\n";

     }
 顯示內容
     textview.setText(n);

    }
   });
   button5.setOnClickListener(new Button.OnClickListener(){
    public void onClick(View v){
     mydaHelper dbh = new mydaHelper(Activity01.this,"my database");
     SQLiteDatabase db = dbh.getWritableDatabase();


刪除表中的內容幾個參數分別是數據庫名字，要刪除的列，列的內容來確定那一列
         db.delete("user", "id=?", new String[]{editText1.getText().toString()});
        }
       });
        }
}</pre>