Sqlite 的小例子

第一步，搞一个数据库帮助类，继承SQLiteOpenHelper类

package com.example.db; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.database.sqlite.SQLiteDatabase.CursorFactory; public class DatabaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "test_user1"; private static final int DATABASE_VERSION= 1; private static final String DATABASE_TABLE = "users"; private static final String DATABASE_CREATE = "create table users(" +"id int," +"names varchar(20)" +")"; /* public DatabaseHelper(Context context){ super(context,DATABASE_NAME,null,DATABASE_VERSION); }*/ public DatabaseHelper(Context context,String name,CursorFactory factory,int version) { super(context,DATABASE_VERSION); } /// 该函数在第一次创建 数据库的时候执行 @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub System.out.println("Create a database test_user and table users"); db.execSQL(DATABASE_CREATE); } @Override public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion) { // TODO Auto-generated method stub db.execSQL("Drop table if exists"+DATABASE_TABLE); onCreate(db); } }

第二步，写一个Activity,用来对数据库实现相关操作

package com.example.Sqlite_test; import com.example.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 Sqlite_test extends Activity { // / 定义变量 private Button createDatabase; private Button updateDatabase; private Button insert; private Button update; private Button query; private Button delete; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); findViews(); setLisensers(); } // /给按钮绑定单击事件监听器 private void setLisensers() { // TODO Auto-generated method stub createDatabase.setOnClickListener(create_Database); updateDatabase.setOnClickListener(update_Database); insert.setOnClickListener(tab_Insert); update.setOnClickListener(tab_update); query.setOnClickListener(tab_query); delete.setOnClickListener(tab_delete); } // / 根据id得到控件对象 private void findViews() { // TODO Auto-generated method stub this.createDatabase = (Button) findViewById(R.id.createDatabase); this.updateDatabase = (Button) findViewById(R.id.updateDatabase); this.insert = (Button) findViewById(R.id.insert); this.update = (Button) findViewById(R.id.update); this.query = (Button) findViewById(R.id.query); this.delete = (Button) findViewById(R.id.delete); } private View.OnClickListener create_Database = new View.OnClickListener() { @Override public void onClick(View v) { // /数据库存在返回true,不存在返回false if (Sqlite_test.this.deleteDatabase("test_user1")) System.out.println("数据已经存在！"); else System.out.println("数据文件不存在！"); // / 生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper( Sqlite_test.this,"test_user1",1); // / 只有调用 了getReadableDatabase方法，或者getWritableDatabase // / 方法，才会创建数据库 databaseHelper.getReadableDatabase(); System.out.println("--------------------—create_Database"); } }; private View.OnClickListener update_Database = new View.OnClickListener() { @Override public void onClick(View v) { // / 生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper( Sqlite_test.this,"test_user.db",2); // / 只有调用 了getReadableDatabase方法，或者getWritableDatabase // / 方法，才会更新数据库 databaseHelper.getReadableDatabase(); System.out.println("--------------------—update_Database"); } }; private View.OnClickListener tab_Insert = 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类型一致 values.put("id",1); values.put("names","wangdan"); // /生成SQLiteDatabase对象 DatabaseHelper dbHelp = new DatabaseHelper(Sqlite_test.this,1); // /调用DatabaseHelper的getWritableDatabase方法，生成 // /SQLiteDatabase对象 SQLiteDatabase db = dbHelp.getWritableDatabase(); // /执行插入 db.insert("users",values); System.out.println("----------------------insert"); } }; private View.OnClickListener tab_update = new View.OnClickListener() { @Override public void onClick(View v) { // /生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper( Sqlite_test.this,1); // /调用 DatabaseHelper对象的getWritableDatabase方法，生成 // /SQLiteDatabase对象 SQLiteDatabase db = databaseHelper.getWritableDatabase(); // /生成ContentValues 对象，并设定键值 对 ContentValues values = new ContentValues(); values.put("names","he shanshan"); // /更新表信息 update user set name='he shanshan' where // / id=1; db.update("users",values,"id=?",new String[] { "1" }); System.out.println("----------------------tab_update"); } }; private View.OnClickListener tab_query = new View.OnClickListener() { @Override public void onClick(View v) { // /生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper( Sqlite_test.this,1); // / 调用databaseHelper的getReadableDatabase()方法 // / 生成SQLiteDatabase对象 SQLiteDatabase db = databaseHelper.getReadableDatabase(); // 执行查询，将查询结果放入到Cursor中 Cursor cursor = db.query("users",new String[] { "id","names" },new String[] { "1" },null); // / 打印查询结果 while (cursor.moveToNext()) { String name = cursor.getString(cursor.getColumnIndex("names")); System.out.println("query name ===>" + name); } } }; private View.OnClickListener tab_delete = new View.OnClickListener() { @Override public void onClick(View v) { // /生成DatabaseHelper对象 DatabaseHelper databaseHelper = new DatabaseHelper( Sqlite_test.this,1); // / 调用 DatabaseHelper对象的 getWritableDatabase()方法 // / 生成 SQLiteDatabase 对象 SQLiteDatabase db = databaseHelper.getWritableDatabase(); db.delete("users",new String[] { "1" }); System.out.println("----------------------tab_delete"); } }; }

第三步，当然不可缺少布局文件，相当简单，就不再贴代码了

第四步，运行结果

05-10 03:43:50.959: INFO/System.out(15420): 数据已经存在！05-10 03:43:51.050: INFO/System.out(15420): Create a database test_user and table users05-10 03:43:51.089: INFO/System.out(15420): --------------------—create_Database05-10 03:44:03.409: INFO/System.out(15420): ----------------------insert05-10 03:44:07.500: INFO/System.out(15420): query name ===>wangdan05-10 03:44:12.690: INFO/System.out(15420): ----------------------tab_update05-10 03:44:13.990: INFO/System.out(15420): query name ===>he shanshan

（编辑：李大同）

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