Android check box and echo

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activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">


    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:text=" Please choose the city you like " />

    <EditText
        android:id="@+id/editText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:ems="10"
        android:inputType="textPersonName"
        android:text=" Your favorite cities are :" />


    <CheckBox
        android:id="@+id/checkBox"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=" Beijing " />

    <CheckBox
        android:id="@+id/checkBox2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=" Shanghai " />

    <CheckBox
        android:id="@+id/checkBox3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=" Hangzhou " />

    <CheckBox
        android:id="@+id/checkBox4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=" sanya " />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="TextView" />

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=" Submit " />

</LinearLayout>

MainActivity.java

package com.example.myapplication;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
   
   
    private CheckBox a,b,c,d;
    private TextView t1,t2;
    private EditText et;
    private Button b1;

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

        a=(CheckBox) findViewById(R.id.checkBox);
        b=(CheckBox) findViewById(R.id.checkBox2);
        c=(CheckBox) findViewById(R.id.checkBox3);
        d=(CheckBox) findViewById(R.id.checkBox4);
         t1=findViewById(R.id.textView);
         t2=findViewById(R.id.textView2);
         et=findViewById(R.id.editText);
         b1=findViewById(R.id.button);
         


        CompoundButton.OnCheckedChangeListener lister=new CompoundButton.OnCheckedChangeListener() {
   
   
           @Override
           public void onCheckedChanged(CompoundButton ckb, boolean isChecked) {
   
   
               if (isChecked){
   
   
                   //Toast.makeText(MainActivity.this,t2+ckb.getText().toString(),Toast.LENGTH_LONG).show();
                  et.setText(" You chose :"+ckb.getText());
               }
           }
       };
        a.setOnCheckedChangeListener(lister);
        b.setOnCheckedChangeListener(lister);
        c.setOnCheckedChangeListener(lister);
        d.setOnCheckedChangeListener(lister);
        b1.setOnClickListener(new View.OnClickListener() {
   
   
            @Override
            public void onClick(View v) {
   
   

     // String splicing to achieve check box echo       If    There are better, simpler    Don't write so much if The judgment statement can    Let me talk to Xiaobai    Thank you very much 
                StringBuffer result=new StringBuffer();
                if(a.isChecked()){
   
   
                    result.append(a.getText()+",");
                }
                if(b.isChecked()){
   
   
                    result.append(b.getText()+",");
                }
                if(c.isChecked()){
   
   
                    result.append(c.getText()+",");
                }
                if(d.isChecked()){
   
   
                    result.append(d.getText()+",");
                }
                t2.setText(result.toString());
            }
        });
       



    }
}