Android studio learning record -- the use of AlertDialog dialog box (ordinary dialog box)

The content area of ​​a normal dialog box generally displays simple text information. It is set by calling the setMessage() method of the AlertDialog.Builder object,

1. Create a program

Create an application called Text062

2. Realize common dialog box through code

details as follows:

MainActivity.java

package com.example.text06;

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

import android.content.DialogInterface;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    @Override
    public void onBackPressed(){
        AlertDialog dialog = null;
        AlertDialog finalDialog = dialog;
        AlertDialog finalDialog1 = dialog;
        AlertDialog.Builder builder = new AlertDialog.Builder(this)
                .setTitle("普通对话框")
                .setIcon(R.mipmap.ic_launcher) 
                .setMessage("Are you sure to exit the application:") 
                .setPositiveButton("OK", new DialogInterface.OnClickListener() { 
                    @Override 
                    public void onClick(DialogInterface dialogInterface, int which) { 
                        finalDialog.dismiss (); 
                        MainActivity.this.finish(); 

                    } 
                }) 
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
                    @Override 
                    } 
                }); 
        dialog = builder.create();
                    public void onClick(DialogInterface dialogInterface, int which) {
                        finalDialog1.dismiss(); 

        dialog.show(); 
    } 
}

activity_main.xml

<?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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

The result of the operation is as follows:

Well, the above is the content of learning.