android_sqlite3实例.docx

Android中Sqlite使用初步 1、使用Sqlite的关键是创建一类，这个类继承SQLiteOpenHelper，继承的类必须重写三个方法：构造方法，onCreate方法，onUpgrate方法 2、SQLiteDatabase是直接操作数据库的对象，可以使用SQLiteOpenHelper的 getReadableDatabase或getWritableDatabase方法得到SQLiteDatabase对象。具体使用这两个方法得到的 SQLiteDatabase对象的不用点，根据方法名就可以看出。一个是得到可读的，一个是得到可写的。 实例代码： 1、布局文件 2、自定义继承SQLiteOpenHelper的类，重写三个方法 package yyl.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class DatabaseHelper extends SQLiteOpenHelper /构造函数 public DatabaseHelper(Context context,String name,CursorFactory factory, int version) super(context,name,factory,version); /该函数在第一次创建数据库的时候执行 Override public void onCreate(SQLiteDatabase db) System.out.println(Creaet a database test_user and table user); db.execSQL(create table user (id int,name varchar(20); Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) System.out.println(upgrate a database); 3、数据库操作代码 package yyl.sqlite;import yyl.db.DatabaseHelper;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.View;import android.widget.Button;public class SqliteActivity extends Activity / 定义变量 private Button createDatabase = null; private Button upgrateDatabase = null; private Button insert = null; private Button update = null; private Button query = null; private Button delete = null; Override public void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState); setContentView(R.layout.main); / 根据ID得到控件对象 createDatabase = (Button) findViewById(R.id.createDatabase); upgrateDatabase = (Button) findViewById(R.id.upgrateDatabase); insert = (Button) findViewById(R.id.insert); update = (Button) findViewById(R.id.update); query = (Button) findViewById(R.id.query); delete = (Button) findViewById(R.id.delete); / 给按钮绑定单击事件监听器 createDatabase.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper(SqliteActivity.this,sqlite_user,null,1); /只有调用了getReadableDatabase方法，或者getWritableDatabase方法，才会创建数据库 databaseHelper.getReadableDatabase(); ); upgrateDatabase.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper(SqliteActivity.this,sqlite_user,null,2); /只有调用了getReadableDatabase方法，或者getWritableDatabase方法，才会更新数据库 databaseHelper.getReadableDatabase(); ); insert.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /创建ContentValue对象 ContentValues values = new ContentValues(); /插入键值对，注意值的类型必须和数据库表中字段的类型一致 values.put(id, 1); values.put(name, yangyulin); /生成SQLiteDatabase对象 DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this,test_user,null,1); SQLiteDatabase db = dbHelper.getWritableDatabase(); /执行插入 db.insert(user, null, values); ); update.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /生成DatabaseHelper对象 DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this,test_user,null,1); /调用DatabaseHelper的getWritableDatabase方法，生成SQLiteDatabase对象 SQLiteDatabase db = dbHelper.getWritableDatabase(); /生成ContentValues对象，并设定键值对 ContentValues values = new ContentValues(); values.put(name, newSky); /更新表信息:update user set name = newSky where id =1; db.update(user, values, id=?, new String1); ); query.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /生成DatabaseHelper对象 DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this,test_user,null,1); /调用DatabaseHelper的getReadableDatabase方法，生成SQLiteDatabase对象 SQLiteDatabase db = dbHelper.getReadableDatabase(); /执行查询，将查询结果放入到Cursor中 Cursor cursor = db.query(user, new Stringid,name, id =?, new String1, null, null, null); /打印查询结果 while(cursor.moveToNext() String name = cursor.getString(cursor.getColumnIndex(name); System.out.println(name - + name); ); delete.setOnClickListener(new View.OnClickListener() Override public void onClick(View v) /生成DatabaseHelper对象 DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this,test_user,null,1); /调用DatabaseHelper的getReadableDatabase方法