5。建库，表，增删改查

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) {

  

    }

}

　　

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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);     } }

　　

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<?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>