第七次Android

<?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:padding="16dp"
    android:orientation="vertical">
    <LinearLayout
        android:layout_marginTop="130dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <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:text="添加"
            android:textSize="18sp"
            android:onClick="add" />
        <Button
            android:id="@+id/btn_query"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="2dp"
            android:layout_weight="1"
            android:background="#DCB5FF"
            android:text="查询"
            android:textSize="18sp"
            android:onClick="serch"/>
        <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:text="修改"
            android:textSize="18sp"
            android:onClick="update"/>
        <Button
            android:id="@+id/btn_delete"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#ACD6FF"
            android:text="删除"
            android:textSize="18sp"
            android:onClick="delete" />
    </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.zsgc;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

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

    @SuppressLint("WrongConstant")
    public void add(View view){
        String name = ((TextView)findViewById(R.id.et_name)).getText().toString();
        int age = Integer.parseInt(((TextView)findViewById(R.id.et_age)).getText().toString());
        StuOpenHelper stuOpenHelper=new StuOpenHelper(this);
        SQLiteDatabase db = stuOpenHelper.getReadableDatabase();
        db.execSQL("insert into student (name,price) values(?,?)",new Object[]{name,age});
        Toast.makeText(this,"ok",0).show();
    }

    public void serch(View view){
        StuOpenHelper stuOpenHelper=new StuOpenHelper(this);
        SQLiteDatabase db = stuOpenHelper.getReadableDatabase();
        String s="";
        Cursor cursor = db.rawQuery("SELECT * from student", null);
        while (cursor.getCount()!=0){
            while (cursor.moveToNext()){
                s+=cursor.getInt(0)+" "+cursor.getInt(1)+" "+cursor.getInt(2)+"
";
            }
        }
        ((TextView)(findViewById(R.id.tv_show))).setText(s);
    }
}

package com.example.zsgc;

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

import androidx.annotation.Nullable;

public class StuOpenHelper extends SQLiteOpenHelper {
    public StuOpenHelper(@Nullable Context context) {
        super(context, "stu.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL("create table student (id integer primary key autoincrement ,name varchar(20),price integer)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}