Android学习笔记 - 数据库篇 (SQLite)

1.SQLite介绍
 官方网站：http://www.sqlite.org/
 
2.SQLiteOpenHelper使用方法
 getReadableDatabase() //创建或打开一个只读的数据库
 getWriteableDatabase() //创建或打开一个可读写的数据库
 onCreate(SQLiteDatabase db) //创建数据库
 onOpen(SQLiteDatabase db) //打开数据库
 onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) //更新数据库
 close() //关闭数据库

 

3.在SQLOpenHelper的子类中，必须有该构造函数
 public DatabaseHelper(Context context, String name, CursorFactory factory, int version)

 

public class DatabaseHelper extends SQLiteOpenHelper {

	// 默认版本
	private static final int VERSION = 1;

	// 默认构造函数
	public DatabaseHelper(Context context, String name, CursorFactory factory, int version) {
		super(context, name, factory, version);
	}

	// 构造函数（用于创建数据库）
	public DatabaseHelper(Context context, String name) {
		this(context, name, null, VERSION);
	}

	// 构造函数（用于更新数据库）
	public DatabaseHelper(Context context, String name, int version) {
		this(context, name, null, version);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		System.out.println("onCreate is start...");
		db.execSQL("create table user( id int, name varchar(20) )");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		System.out.println("onUpgrade is start...");
	}
}

 

4.使用adb访问SQLite
 adb shell //进行linux命令行（调试环境）
 ls -l //相当于dir /w
 cd data //与cd相同
 sqlite3 dbname //进入SQL管理模式
 .schema //查看数据库中的表
 SQL语句 //可直接查询
 rm -r databases //循环删除目录

5.增、删、改、查

public class SQLiteActivity extends Activity {

	// 声明控件
	private Button btnCreate = null;
	private Button btnUpgrade = null;
	private Button btnInsert = null;
	private Button btnUpdate = null;
	private Button btnDelete = null;
	private Button btnSelect = null;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.sqlite);

		// 寻找控件
		btnCreate = (Button) findViewById(R.id.btnCreateDb);
		btnUpgrade = (Button) findViewById(R.id.btnUpgradeDb);
		btnInsert = (Button) findViewById(R.id.btnInsertDb);
		btnUpdate = (Button) findViewById(R.id.btnUpdateDb);
		btnDelete = (Button) findViewById(R.id.btnDeleteDb);
		btnSelect = (Button) findViewById(R.id.btnSelectDb);

		// 创建数据库
		btnCreate.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnCreate on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
				helper.getReadableDatabase();
			}
		});

		// 更新数据库
		btnUpgrade.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnUpgrade on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb", 2);
				helper.getReadableDatabase();
			}
		});

		// 新增数据
		btnInsert.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnInsert on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
				SQLiteDatabase db = helper.getWritableDatabase();

				// 参数列表
				ContentValues params = new ContentValues();
				params.put("id", 1);
				params.put("name", "dier");

				// 表名、列名、参数列表
				db.insert("user", null, params);
			}
		});

		// 修改数据
		btnUpdate.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnUpdate on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
				SQLiteDatabase db = helper.getWritableDatabase();

				// 参数列表
				ContentValues params = new ContentValues();
				params.put("name", "stdier");

				// 表名、参数列表、WHERE子句、子句参数
				db.update("user", params, "id=?", new String[] { "1" });
			}
		});

		// 删除数据
		btnDelete.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnDelete on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
				SQLiteDatabase db = helper.getWritableDatabase();

				// 表名、列名、参数列表
				db.delete("user", "id=?", new String[] { "1" });
			}
		});

		// 修改数据
		btnSelect.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				System.out.println("btnSelect on start...");
				DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
				SQLiteDatabase db = helper.getWritableDatabase();

				//表名、查询字段、WHERE子句、子句参数、groupBy、having、orderBy
				Cursor cursor = db.query("user", new String[] { "id", "name" }, "id=?", new String[] { "1" }, null, null, null);
				while (cursor.moveToNext()) {
					System.out.println("query name -> " + cursor.getString(cursor.getColumnIndex("name")));
				}
			}
		});
	}
}