Android数据库增删改查

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


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

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

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


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

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

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


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

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

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

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

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

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

</LinearLayout>

package com.example.myapplication;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
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);
    }

    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());

        db.execSQL("insert into stuinfo (name,age) values(?,?)", new Object[]{
                name, age});
        Toast.makeText(this, "添加成功", Toast.LENGTH_SHORT).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", Toast.LENGTH_SHORT).show();

    }

    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", Toast.LENGTH_SHORT).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.myapplication;

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

    }

}