增删改查的实现

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:padding="16dp" android:orientation="vertical" android:background="@drawable/bg" 
android:layout_height="match_parent" android:layout_width="match_parent" xmlns:android="http://schemas.android.com/apk/res/android">


    <LinearLayout android:layout_height="wrap_content" android:layout_width="match_parent" android:layout_marginTop="130dp">

        <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:textSize="18sp" android:text="姓 名 ："/>

        <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:textSize="16sp" android:hint="请输入姓名" 
            android:id="@+id/et_name"/>

    </LinearLayout>


    -<LinearLayout android:layout_height="wrap_content" android:layout_width="match_parent" android:layout_marginBottom="10dp">

    <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:textSize="18sp" android:text="年 龄："/>

    <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:textSize="16sp" android:hint="输入年龄" android:id="@+id/et_age"/>

</LinearLayout>


    -<LinearLayout android:layout_height="wrap_content" android:layout_width="match_parent">

    <Button android:background="#B9B9FF" android:layout_height="wrap_content" android:layout_width="0dp" 
      android:textSize="18sp" android:text="添加" android:id="@+id/btn_add" android:onClick="add" android:layout_weight="1" android:layout_marginRight="2dp"/>

    <Button android:background="#DCB5FF" android:layout_height="wrap_content" android:layout_width="0dp" 
      android:textSize="18sp" android:text="查询" android:id="@+id/btn_query" android:onClick="search" android:layout_weight="1" android:layout_marginRight="2dp"/>

    <Button android:background="#E6CAFF" android:layout_height="wrap_content" android:layout_width="0dp" 
       android:textSize="18sp" android:text="修改" android:id="@+id/btn_update" android:onClick="update" android:layout_weight="1" android:layout_marginRight="2dp"/>

    <Button android:background="#ACD6FF" android:layout_height="wrap_content" android:layout_width="0dp" 
       android:textSize="18sp" android:text="删除" android:id="@+id/btn_delete" android:onClick="delete" android:layout_weight="1"/>

</LinearLayout>


    -<ScrollView android:layout_height="wrap_content" android:layout_width="match_parent">

    <TextView android:layout_height="wrap_content" android:layout_width="match_parent" android:layout_marginTop="25dp" 
         android:textSize="20sp" android:id="@+id/tv_show"/>

</ScrollView>

</LinearLayout>

package com.example.android;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @SuppressLint("WrongConstant")
    public void add(View v) {
        StuOpenHelper helper = new StuOpenHelper(this);
        SQLiteDatabase db = helper.getWritableDatabase();
        String name = ((EditText) findViewById(R.id.et_name)).getText()
                .toString();
        int age = Integer.parseInt(((EditText) findViewById(R.id.et_age))
                .getText().toString());

        // 原生sql操作,
        // db.execSQL("insert into stuinfo (name,age) values('lisi',22)");
        // db.execSQL("insert into stuinfo (name,age) values(?,?)",new
        // Object[]{"kitty",30});
        db.execSQL("insert into stuinfo (name,age) values(?,?)", new Object[] {
                name, age });
        Toast.makeText(this, "ok", 0).show();

    }

    public void delete(View view) {
        StuOpenHelper helper = new StuOpenHelper(this);
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("delete from stuinfo where _id=?", new Object[] { 2 });
        Toast.makeText(this, "删除成功", 0).show();

    }

    @SuppressLint("WrongConstant")
    public void update(View view) {
        StuOpenHelper helper = new StuOpenHelper(this);
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("update stuinfo set name=? where _id=?", new Object[] {
                "micky", 3 });
        Toast.makeText(this, "修改成功", 0).show();

    }

    public void search(View view) {
        StuOpenHelper helper = new StuOpenHelper(this);
        SQLiteDatabase db = helper.getWritableDatabase();
        String s = "";
        Cursor cursor = db.rawQuery("select * from stuinfo", null);
        if (cursor.getCount() != 0) {

            while (cursor.moveToNext()) {
                s += cursor.getInt(0) + "   " + cursor.getString(1) + "   "
                        + cursor.getInt(2) + "
";
            }
        }

        // Toast.makeText(this, s, 0).show();
        ((TextView) (findViewById(R.id.tv_show))).setText(s);

    }

}

package com.example.android;

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

public class StuOpenHelper extends SQLiteOpenHelper {

    public StuOpenHelper(Context context) {
        super(context, "stu.db", null, 1);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        db.execSQL("create table stuinfo(_id integer primary key autoincrement,name varchar(20),age integer)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub

    }

}