创建数据库类实现 增删改查功能

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
* Created by han shan on 2016/5/25.
*/
public class DBOpenHelper extends SQLiteOpenHelper{
DBOpenHelper (Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);   //必须通过super调用父类构造函数
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS person ("
+ "id INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "name VARCHAR(20),"
+ "age SMALLINT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS person");
onCreate(db);
}

}

public class Person {
public int id;
public String name;
public int age;

public Person() {
}

public Person(String name, int age) {
this.name = name;
this.age = age;
}
}

case R.id.btn :
//创建辅助类对象
DBOpenHelper helper = new DBOpenHelper(getApplicationContext(), "test.db", null,DB_VERSION);
//调用getWritableDatabase()或getReadableDatabase()才会真正创建或打开
SQLiteDatabase db=helper.getWritableDatabase();
db.close(); //操作完成后关闭数据库连接
Toast.makeText(getApplicationContext(), "数据库创建成功", Toast.LENGTH_SHORT).show();
break;

case R.id.btn1:
DBOpenHelper helper1 = new DBOpenHelper(getApplicationContext(), "test.db", null,DB_VERSION);
SQLiteDatabase db1=helper1.getWritableDatabase();
Person person = new Person();
person.name = "wustzz";
person.age = 39;
db1.execSQL("INSERT INTO person VALUES (NULL, ?, ?)",
new Object[ ] { person.name, person.age } );

db1.close();    //数据操作完毕一定要记得关闭数据库连接
Toast.makeText(getApplicationContext(), "记录添加成功", Toast.LENGTH_SHORT).show();
break;

case R.id.btn2:
DBOpenHelper helper2 = new DBOpenHelper(getApplicationContext(), "test.db", null,DB_VERSION);
SQLiteDatabase db2=helper2.getWritableDatabase();
//删除数据
db2.execSQL( "Delete from person where age<?", new Object[ ]{ "40" } );
db2.close();    //关闭数据库连接
Toast.makeText(getApplicationContext(), "记录删除成功", Toast.LENGTH_SHORT).show();
break;

case R.id.btn3:
DBOpenHelper helper3 = new DBOpenHelper(getApplicationContext(), "test.db", null,DB_VERSION);
SQLiteDatabase db3=helper3.getWritableDatabase();
//更新数据
db3.execSQL("Update person set age=? where name like ?",
new Object[ ]{ 20,"wust%" } );
db3.close();    //关闭数据库连接
Toast.makeText(getApplicationContext(), "记录修改成功", Toast.LENGTH_SHORT).show();
break;

case R.id.btn4:
DBOpenHelper helper4 = new DBOpenHelper(getApplicationContext(), "test.db", null,DB_VERSION);
SQLiteDatabase db4=helper4.getWritableDatabase();
Cursor cursor = db4.rawQuery( "SELECT * FROM person where age>?",  new String[]{"10"} );

TextView tv=(TextView)findViewById(R.id.tv);   //简单用TextView显示数据
tv.setText("查询到"+cursor.getCount()+"条记录(当前数据库版本号="+DB_VERSION+")");
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id") );
String name = cursor.getString(cursor.getColumnIndex("name") );
int age = cursor.getInt(cursor.getColumnIndex("age") );
tv.setText(tv.getText()+"\n"+"id="+id+",name="+name+",age="+age);
}
cursor.close();   //关闭cursor
db4.close();  //关闭数据库连接

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="数据库创建"
android:id="@+id/btn" />

<Button
android:layout_width="350dp"
android:layout_height="wrap_content"
android:text="增加记录"
android:id="@+id/btn1"
android:layout_gravity="right" />

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="删除记录"
android:id="@+id/btn2" />

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="修改记录"
android:id="@+id/btn3"
android:layout_gravity="center_horizontal" />

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="查询记录"
android:id="@+id/btn4"
android:layout_gravity="center_horizontal" />

<TextView
android:layout_width="350dp"
android:layout_height="wrap_content"
android:text="New Text"
android:id="@+id/tv"
android:layout_weight="0.85" />