[Android] SQLite數據庫之增刪改查基礎操作

在編程中經常會遇到數據庫的操作,而Android系統內置了SQLite,它是一款輕型數據庫,遵守事務ACID的關系型數據庫管理系統,它占用的資源非常低,能夠支持Windows/Linux/Unix等主流操作系統,同時能夠跟很多程序語言如C#、PHP、Java等相結合.下面先回顧SQL的基本語句,再講述Android的基本操作.

一. adb shell回顧SQL語句

首先,我感覺自己整個大學印象最深的幾門課就包括《數據庫》,所以想先回顧SQL增刪改查的基本語句.而在Android SDK中adb是自帶的調試工具,它存放在sdk的platform-tools目錄下,通過adb shell可以進入設備控制台,操作SQL語句.

G:
cd G:\software\Program software\Android\adt-bundle-windows-x86_64-20140321\sdk\platform-tools
adb shell
cd /data/data/com.example.sqliteaction/databases/
sqlite3 StuDatabase.db
.table
.schema

--創建Teacher表
create table Teacher (id integer primary key, name text);
--向表中插入數據
insert into Teacher (id,name) values('10001', 'Mr Wang');
insert into Teacher (id,name) values('10002', 'Mr Yang');
--查詢數據
select * from Teacher;
--更新數據
update Teacher set name='Yang XZ' where id=10002;
--刪除數據
delete from Teacher where id=10001;

二. SQLite數據庫操作

下面講解使用SQLite操作數據庫:
1.創建打開數據庫
使用openOrCreateDatabase函數實現,它會自動檢測是否存在該數據庫,如果存在則打開,否則創建一個數據庫,並返回一個SQLiteDatabase對象.
2.創建表
通過定義建表的SQL語句,再調用execSQL方法執行該SQL語句實現建立表.

//創建學生表(學號,姓名,電話,身高) 主鍵學號
public static final String createTableStu = "create table Student (" +
		"id integer primary key, " +
		"name text, " +
		"tel text, " +
		"height real)";
//SQLiteDatabase定義db變量
db.execSQL(createTableStu);

//方法一
SQLiteDatabase db = sqlHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("id", "10001");
values.put("name", "Eastmount");
values.put("tel", "15201610000");
values.put("height", "172.5");
db.insert("Student", null, values);
//方法二
public static final String insertData = "insert into Student (" +
		"id, name, tel, height) values('10002','XiaoMing','110','175')";
db.execSQL(insertData);

//方法一 刪除身高>175cm
SQLiteDatabase db = sqlHelper.getWritableDatabase();
db.delete("Student", "height > ?", new String[] {"175"});
//方法二
String deleteData = "DELETE FROM Student WHERE height>175";
db.execSQL(deleteData);

//小明的身高修改為180
SQLiteDatabase db = sqlHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("height", "180");
db.update("Student", values, "name = ?", new String[] {"XiaoMing"});

下面是關於數據庫的其他操作,其中包括使用SQL語句執行,而查詢數據Query方法由於涉及ListView顯示,請見具體實例.

//關閉數據庫
SQLiteDatabase.close();
//刪除表 執行SQL語句
SQLiteDatabase.execSQL("DROP TABLE Student");
//刪除數據庫
this.deleteDatabase("StuDatabase.db");
//查詢數據
SQLiteDatabase.query();

三. 數據庫操作簡單實例

顯示效果如下圖所示：

首先，添加activity_main.xml文件布局如下：

再次,添加自定義類MySQLiteOpenHelper：

//添加自定義類 繼承SQLiteOpenHelper
public class MySQLiteOpenHelper extends SQLiteOpenHelper {

	public Context mContext;
	
	//創建學生表(學號,姓名,電話,身高) 主鍵學號
	public static final String createTableStu = "create table Student (" +
			"id integer primary key, " +
			"name text, " +
			"tel text, " +
			"height real)";
	
	//抽象類 必須定義顯示的構造函數 重寫方法 
	public MySQLiteOpenHelper(Context context, String name, CursorFactory factory, 
			int version) {
		super(context, name, factory, version);
		mContext = context;
	}
	
	@Override
	public void onCreate(SQLiteDatabase arg0) {
		// TODO Auto-generated method stub
		arg0.execSQL(createTableStu);
		Toast.makeText(mContext, "Created", Toast.LENGTH_SHORT).show();		
	}
	
	@Override
	public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
		// TODO Auto-generated method stub
		arg0.execSQL("drop table if exists Student");
		onCreate(arg0);
		Toast.makeText(mContext, "Upgraged", Toast.LENGTH_SHORT).show();
	}
}

public class MainActivity extends Activity {
	
	//繼承SQLiteOpenHelper類
	private MySQLiteOpenHelper sqlHelper;
	private ListView listview;
	private EditText edit1;
	private EditText edit2;
	private EditText edit3;
	private EditText edit4;
	
	@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sqlHelper = new MySQLiteOpenHelper(this, "StuDatabase.db", null, 2);
        //建立新表
        Button createBn = (Button) findViewById(R.id.button1);
        createBn.setOnClickListener(new OnClickListener() {
        	@Override
        	public void onClick(View v) {
        		sqlHelper.getWritableDatabase();
        	}
        });
        //插入數據
        Button insertBn = (Button) findViewById(R.id.button2);
        edit1 = (EditText) findViewById(R.id.edit_id);
        edit2 = (EditText) findViewById(R.id.edit_name);
        edit3 = (EditText) findViewById(R.id.edit_tel);
        edit4 = (EditText) findViewById(R.id.edit_height);
        insertBn.setOnClickListener(new OnClickListener() {
        	@Override
        	public void onClick(View v) {
        		SQLiteDatabase db = sqlHelper.getWritableDatabase();
        		ContentValues values = new ContentValues();
        		/*
        		//插入第一組數據
        		values.put("id", "10001");
        		values.put("name", "Eastmount");
        		values.put("tel", "15201610000");
        		values.put("height", "172.5");
        		db.insert("Student", null, values);
        		*/
        		values.put("id", edit1.getText().toString());
        		values.put("name", edit2.getText().toString());
        		values.put("tel", edit3.getText().toString());
        		values.put("height", edit4.getText().toString());
        		db.insert("Student", null, values);
        		Toast.makeText(MainActivity.this, "數據插入成功", Toast.LENGTH_SHORT).show();
        		edit1.setText("");
        		edit2.setText("");
        		edit3.setText("");
        		edit4.setText("");
        	}
        });
        //刪除數據
        Button deleteBn = (Button) findViewById(R.id.button3);
        deleteBn.setOnClickListener(new OnClickListener() {
        	@Override
        	public void onClick(View v) {
        		SQLiteDatabase db = sqlHelper.getWritableDatabase();
        		db.delete("Student", "height > ?", new String[] {"180"});
        		Toast.makeText(MainActivity.this, "刪除數據", Toast.LENGTH_SHORT).show();
        	}
        });
        //更新數據
        Button updateBn = (Button) findViewById(R.id.button4);
        updateBn.setOnClickListener(new OnClickListener() {
        	@Override
        	public void onClick(View v) {
        		SQLiteDatabase db = sqlHelper.getWritableDatabase();
        		ContentValues values = new ContentValues();
        		values.put("height", "180");
        		db.update("Student", values, "name = ?", new String[] {"XiaoMing"});
        		Toast.makeText(MainActivity.this, "更新數據", Toast.LENGTH_SHORT).show();
        	}
        });
        //查詢數據
        listview = (ListView) findViewById(R.id.listview1);
        Button selectBn = (Button) findViewById(R.id.button5);
        selectBn.setOnClickListener(new OnClickListener() {
        	@Override
        	public void onClick(View v) {
        		try {
	        		SQLiteDatabase db = sqlHelper.getWritableDatabase();
	        		//游標查詢每條數據
	        		Cursor cursor = db.query("Student", null, null, null, null, null, null);
	        		//定義list存儲數據
	        		List> list = new ArrayList>();
	        		//適配器SimpleAdapter數據綁定
	        		//錯誤:構造函數SimpleAdapter未定義 需把this修改為MainActivity.this
	        		SimpleAdapter adapter = new SimpleAdapter(MainActivity.this, list, R.layout.stu_item,
	        				new String[]{"id", "name", "tel", "height"}, 
	        				new int[]{R.id.stu_id, R.id.stu_name, R.id.stu_tel, R.id.stu_height});
	        		//讀取數據 游標移動到下一行
	        		while(cursor.moveToNext()) {
	        			Map map = new HashMap();
	        			map.put( "id", cursor.getString(cursor.getColumnIndex("id")) );
	        			map.put( "name", cursor.getString(cursor.getColumnIndex("name")) );
	        			map.put( "tel", cursor.getString(cursor.getColumnIndex("tel")) );
	        			map.put( "height", cursor.getString(cursor.getColumnIndex("height")) );
	        			list.add(map);
	        		}
	        		listview.setAdapter(adapter);
        		}
        		catch (Exception e){
        			Log.i("exception", e.toString());
        		}
        	}
        });
    }
}