[Java] Handler vs runOnUiThread vs AsyncTask

Handler.post()   vs   runOnUiThread()   vs   AsyncTask.execute()

---

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:id="@+id/tvText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Ready"
        android:textSize="34dp"
        android:textStyle="bold"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/btnHandler"
        android:layout_width="200dp"
        android:layout_height="80dp"
        android:textAllCaps="false"
        android:text="Handler.post()"
        android:textSize="18dp"
        android:layout_marginTop="30dp"
        app:layout_constraintTop_toBottomOf="@+id/tvText"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btnRunOnUiThread"
        android:layout_width="200dp"
        android:layout_height="80dp"
        android:textAllCaps="false"
        android:text="runOnUiThread()"
        android:textSize="18dp"
        app:layout_constraintTop_toBottomOf="@+id/btnHandler"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btnAsyncTask"
        android:layout_width="200dp"
        android:layout_height="80dp"
        android:textAllCaps="false"
        android:text="AsyncTast.execute()"
        android:textSize="18dp"
        app:layout_constraintTop_toBottomOf="@+id/btnRunOnUiThread"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

 

 

 

 

 

 

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;

import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    TextView tvText;
    Button btnHandler;
    Button btnRunOnUiThread;
    Button btnAsyncTask;

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

        tvText = findViewById(R.id.tvText);
        btnHandler = findViewById(R.id.btnHandler);
        btnRunOnUiThread = findViewById(R.id.btnRunOnUiThread);
        btnAsyncTask = findViewById(R.id.btnAsyncTask);

        final Handler handler = new Handler();
        btnHandler.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        tvText.setText("Handler.post() 클릭");
                    }
                });
            }
        });

        btnRunOnUiThread.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        tvText.setText("runOnUiThread() 클릭");
                    }
                });
            }
        });

        btnAsyncTask.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AsyncTask.execute(new Runnable() {
                    @Override
                    public void run() {
                        tvText.setText("AsyncTask.execute() 클릭");
                    }
                });
            }
        });
    }

}

실행 결과

 

 

AsyncTask.execute() 버튼 클릭 후 에러 발생!

AsyncTask.execute() 버튼 클릭 후 에러 발생

AsyncTask.execute()는 UI 작업을 할 수 없다.

AsyncTask는 기본으로 doInBackground()에서 돌아가기 때문이다.