Android SQLite database practice

SQLite Database actual combat project

Add ： Because of the need to recyclerview Control , For specific use, please refer to

Android- Section 7 RecyclerView Detailed explanation

1. Build table

MySQLiteOpenHelper The entity class

package com.hnucm.a_test133;

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

import androidx.annotation.Nullable;

public class MySQLiteOpenHelper extends SQLiteOpenHelper {
    public MySQLiteOpenHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql="create table student(id integer primary key autoincrement,stuid varchar(50), stuname varchar(20),stuclass varchar(20))";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

stay activity in

package com.hnucm.a_test133;

import androidx.appcompat.app.AppCompatActivity;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteOpenHelper mySQLiteOpenHelper=new MySQLiteOpenHelper(this,"students.db",null,1);
        SQLiteDatabase sqLiteDatabase=mySQLiteOpenHelper.getWritableDatabase();
    }
}

2. To write ui

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <EditText
        android:id="@+id/editTextTextPersonName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="10dp"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint=" Please enter the student number "
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editTextTextPersonName2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint=" Please enter a name "
        app:layout_constraintStart_toStartOf="@+id/editTextTextPersonName"
        app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName" />

    <EditText
        android:id="@+id/editTextTextPersonName3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint=" Please enter class "
        app:layout_constraintStart_toStartOf="@+id/editTextTextPersonName2"
        app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName2" />

    <EditText
        android:id="@+id/editTextTextPersonName4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint=" Search for student information "
        app:layout_constraintStart_toStartOf="@+id/editTextTextPersonName3"
        app:layout_constraintTop_toBottomOf="@+id/editTextTextPersonName3" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=" Add students "
        app:layout_constraintBottom_toBottomOf="@+id/editTextTextPersonName3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName3" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=" Ask the students "
        app:layout_constraintBottom_toBottomOf="@+id/editTextTextPersonName4"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/editTextTextPersonName4" />
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recylerview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintTop_toBottomOf="@id/button2"
        app:layout_constraintBottom_toBottomOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>

Available by operation students.db file

3. Set the add data button

package com.hnucm.a_test133;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    EditText editText;
    EditText editText2;
    EditText editText3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteOpenHelper mySQLiteOpenHelper=new MySQLiteOpenHelper(this,"students.db",null,1);
        SQLiteDatabase sqLiteDatabase=mySQLiteOpenHelper.getWritableDatabase();

        editText=findViewById(R.id.editTextTextPersonName);
        editText2=findViewById(R.id.editTextTextPersonName2);
        editText3=findViewById(R.id.editTextTextPersonName3);
        Button button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues contentValues=new ContentValues();
                contentValues.put("stuid",editText.getText().toString());
                contentValues.put("stuname",editText2.getText().toString());
                contentValues.put("stuclass",editText3.getText().toString());

                sqLiteDatabase.insert("student",null,contentValues);
                Toast.makeText(MainActivity.this," Increase student success ",Toast.LENGTH_LONG).show();
            }
        });
    }
}

4. add to Recyclerview View

First , Before, I added Recyclerview Control , One more needs to be built item Layout file

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="150dp">


    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="42dp"
        android:layout_marginLeft="42dp"
        android:text="TextView"
        app:layout_constraintBottom_toTopOf="@+id/textView2"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="@+id/textView2"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintBottom_toTopOf="@+id/textView3"
        app:layout_constraintStart_toStartOf="@+id/textView"
        app:layout_constraintTop_toBottomOf="@+id/textView" />



</androidx.constraintlayout.widget.ConstraintLayout>

The second step ： Create entity class

The third step ： To write myholder,myadapter And the assignment

package com.hnucm.a_test133;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    EditText editText;
    EditText editText2;
    EditText editText3;
    RecyclerView recyclerView;
    List<Student> list=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteOpenHelper mySQLiteOpenHelper=new MySQLiteOpenHelper(this,"students.db",null,1);
        SQLiteDatabase sqLiteDatabase=mySQLiteOpenHelper.getWritableDatabase();

        editText=findViewById(R.id.editTextTextPersonName);
        editText2=findViewById(R.id.editTextTextPersonName2);
        editText3=findViewById(R.id.editTextTextPersonName3);

        recyclerView=findViewById(R.id.recylerview);// Instantiation 

        Cursor cursor=sqLiteDatabase.query("student",null,null,null,null,null,null);// It means to get the data of all fields 
        while (cursor.moveToNext()){//cursor The cursor defaults to the first line , Data can be obtained by moving the cursor 
            Student student=new Student();

            // Sometimes it is necessary to modify multiple identical field names at the same time   You can hold down the alt+shift+r
            // Fetch data through cursor 
            student.id=cursor.getInt(0);
            student.stuid=cursor.getString(1);
            student.stuname=cursor.getString(2);
            student.stuclass=cursor.getString(3);

            list.add(student);
        }
        cursor.close();// close cursor, Prevent memory leaks 
        recyclerView.setAdapter(new MyAdapter());
        // Express RecyclerView Arrange in a linear way , One line shows one 
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        Button button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues contentValues=new ContentValues();
                contentValues.put("stuid",editText.getText().toString());
                contentValues.put("stuname",editText2.getText().toString());
                contentValues.put("stuclass",editText3.getText().toString());

                sqLiteDatabase.insert("Student",null,contentValues);
                Toast.makeText(MainActivity.this," Increase student success ",Toast.LENGTH_LONG).show();
            }
        });
    }
    public class MyAdapter extends RecyclerView.Adapter<MyHolder>{

        @NonNull
        @Override
        public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view= LayoutInflater.from(MainActivity.this).inflate(R.layout.item,parent,false);// load view
            MyHolder myHolder=new MyHolder(view);// return view
            return myHolder;
        }

        @Override
        public void onBindViewHolder(@NonNull MyHolder holder, int position) {

            Student student=list.get(position);

            holder.textView.setText(" Student number : "+student.stuid);
            holder.textView1.setText(" full name : "+student.stuname);
            holder.textView2.setText(" class : "+student.stuclass);
        }

        @Override
        public int getItemCount() {
            return list.size();
        }

    }
    public class MyHolder extends RecyclerView.ViewHolder{
        TextView textView;// Member variables 
        TextView textView1;
        TextView textView2;
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            textView=itemView.findViewById(R.id.textView);
            textView1=itemView.findViewById(R.id.textView2);
            textView2=itemView.findViewById(R.id.textView3);
        }
    }
}

function ：

But every time you add data, you just add it to the database , Our list will not refresh the data , So we need to add data to the list every time we click add data

package com.hnucm.a_test133;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    EditText editText;
    EditText editText2;
    EditText editText3;
    RecyclerView recyclerView;
    MyAdapter myAdapter;
    List<Student> list=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteOpenHelper mySQLiteOpenHelper=new MySQLiteOpenHelper(this,"students.db",null,1);
        SQLiteDatabase sqLiteDatabase=mySQLiteOpenHelper.getWritableDatabase();

        editText=findViewById(R.id.editTextTextPersonName);
        editText2=findViewById(R.id.editTextTextPersonName2);
        editText3=findViewById(R.id.editTextTextPersonName3);

        recyclerView=findViewById(R.id.recylerview);// Instantiation 

        Cursor cursor=sqLiteDatabase.query("student",null,null,null,null,null,null);// It means to get the data of all fields 
        while (cursor.moveToNext()){//cursor The cursor defaults to the first line , Data can be obtained by moving the cursor 
            Student student=new Student();

            // Sometimes it is necessary to modify multiple identical field names at the same time   You can hold down the alt+shift+r
            // Fetch data through cursor 
            student.id=cursor.getInt(0);
            student.stuid=cursor.getString(1);
            student.stuname=cursor.getString(2);
            student.stuclass=cursor.getString(3);

            list.add(student);
        }
        cursor.close();// close cursor, Prevent memory leaks 
        myAdapter = new MyAdapter();
        recyclerView.setAdapter(myAdapter);
        // Express RecyclerView Arrange in a linear way , One line shows one 
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        Button button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues contentValues=new ContentValues();
                contentValues.put("stuid",editText.getText().toString());
                contentValues.put("stuname",editText2.getText().toString());
                contentValues.put("stuclass",editText3.getText().toString());

                long id = sqLiteDatabase.insert("student", null, contentValues);

                Student student=new Student();
                student.stuid=editText.getText().toString();
                student.stuname=editText2.getText().toString();
                student.stuclass=editText3.getText().toString();
                student.id= (int) id;
                list.add(student);
                myAdapter.notifyDataSetChanged();

                Toast.makeText(MainActivity.this," Increase student success ",Toast.LENGTH_LONG).show();


            }
        });
    }
    public class MyAdapter extends RecyclerView.Adapter<MyHolder>{

        @NonNull
        @Override
        public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view= LayoutInflater.from(MainActivity.this).inflate(R.layout.item,parent,false);// load view
            MyHolder myHolder=new MyHolder(view);// return view
            return myHolder;
        }

        @Override
        public void onBindViewHolder(@NonNull MyHolder holder, int position) {

            Student student=list.get(position);

            holder.textView.setText(" Student number : "+student.stuid);
            holder.textView1.setText(" full name : "+student.stuname);
            holder.textView2.setText(" class : "+student.stuclass);
        }

        @Override
        public int getItemCount() {
            return list.size();
        }

    }

    public class MyHolder extends RecyclerView.ViewHolder{
        TextView textView;// Member variables 
        TextView textView1;
        TextView textView2;
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            textView=itemView.findViewById(R.id.textView);
            textView1=itemView.findViewById(R.id.textView2);
            textView2=itemView.findViewById(R.id.textView3);
        }
    }
}

function , You can see that we didn't load data at the beginning of the pull-down refresh , After clicking the button, a new piece of data is added

5. Set query data button

package com.hnucm.a_test133;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    EditText editText;
    EditText editText2;
    EditText editText3;
    EditText editText4;
    RecyclerView recyclerView;
    MyAdapter myAdapter;
    List<Student> list=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MySQLiteOpenHelper mySQLiteOpenHelper=new MySQLiteOpenHelper(this,"students.db",null,1);
        SQLiteDatabase sqLiteDatabase=mySQLiteOpenHelper.getWritableDatabase();

        editText=findViewById(R.id.editTextTextPersonName);
        editText2=findViewById(R.id.editTextTextPersonName2);
        editText3=findViewById(R.id.editTextTextPersonName3);
        editText4=findViewById(R.id.editTextTextPersonName4);
        recyclerView=findViewById(R.id.recylerview);// Instantiation 

        Cursor cursor=sqLiteDatabase.query("student",null,null,null,null,null,null);// It means to get the data of all fields 
        while (cursor.moveToNext()){//cursor The cursor defaults to the first line , Data can be obtained by moving the cursor 
            Student student=new Student();

            // Sometimes it is necessary to modify multiple identical field names at the same time   You can hold down the alt+shift+r
            // Fetch data through cursor 
            student.id=cursor.getInt(0);
            student.stuid=cursor.getString(1);
            student.stuname=cursor.getString(2);
            student.stuclass=cursor.getString(3);

            list.add(student);
        }
        cursor.close();// close cursor, Prevent memory leaks 
        myAdapter = new MyAdapter();
        recyclerView.setAdapter(myAdapter);
        // Express RecyclerView Arrange in a linear way , One line shows one 
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        Button button1=findViewById(R.id.button2);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                list.clear();// Empty data 
                String content="%"+editText4.getText().toString()+"%";
                //like  Represents a fuzzy match    where stuname like %name%
                Cursor cursor= sqLiteDatabase.query("student",null,"stuclass like ?",new  String[]{content},null,null,null);// It means to get the data of all fields 
                while (cursor.moveToNext()) {//cursor The cursor defaults to the first line , Data can be obtained by moving the cursor 
                    Student student=new Student();
                    // Fetch data through cursor 
                    student.id=cursor.getInt(0);
                    student.stuid=cursor.getString(1);
                    student.stuname=cursor.getString(2);
                    student.stuclass=cursor.getString(3);
                    list.add(student);

                }
                cursor.close();// close cursor, Prevent memory leaks 
                myAdapter.notifyDataSetChanged();// Interface update 

            }
        });

        Button button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues contentValues=new ContentValues();
                contentValues.put("stuid",editText.getText().toString());
                contentValues.put("stuname",editText2.getText().toString());
                contentValues.put("stuclass",editText3.getText().toString());

                long id = sqLiteDatabase.insert("student", null, contentValues);

                Student student=new Student();
                student.stuid=editText.getText().toString();
                student.stuname=editText2.getText().toString();
                student.stuclass=editText3.getText().toString();
                student.id= (int) id;
                list.add(student);
                myAdapter.notifyDataSetChanged();

                Toast.makeText(MainActivity.this," Increase student success ",Toast.LENGTH_LONG).show();


            }
        });
    }
    public class MyAdapter extends RecyclerView.Adapter<MyHolder>{

        @NonNull
        @Override
        public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view= LayoutInflater.from(MainActivity.this).inflate(R.layout.item,parent,false);// load view
            MyHolder myHolder=new MyHolder(view);// return view
            return myHolder;
        }

        @Override
        public void onBindViewHolder(@NonNull MyHolder holder, int position) {

            Student student=list.get(position);

            holder.textView.setText(" Student number : "+student.stuid);
            holder.textView1.setText(" full name : "+student.stuname);
            holder.textView2.setText(" class : "+student.stuclass);
        }

        @Override
        public int getItemCount() {
            return list.size();
        }

    }

    public class MyHolder extends RecyclerView.ViewHolder{
        TextView textView;// Member variables 
        TextView textView1;
        TextView textView2;
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            textView=itemView.findViewById(R.id.textView);
            textView1=itemView.findViewById(R.id.textView2);
            textView2=itemView.findViewById(R.id.textView3);
        }
    }
}

function ：

Fuzzy matching multiple fields ：

Cursor cursor= sqLiteDatabase.query("student",null,"stuclass like ? or stuid like ?",new  String[]{content,content},null,null,null);// It means to get the data of all fields