[Java] AsyncTask

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="30dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/btnStart"
        android:layout_width="180dp"
        android:layout_height="80dp"
        android:textAllCaps="false"
        android:text="Start"
        android:textSize="16dp"
        android:layout_marginTop="30dp"
        app:layout_constraintTop_toBottomOf="@+id/tvText"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

 

 

 

 

 

MyAsyncTask.java

package com.jwsoft.javaproject;

import android.os.AsyncTask;
import android.widget.TextView;

public class MyAsyncTask extends AsyncTask<Void, Integer, Boolean> {

    TextView tvText;

    public MyAsyncTask(TextView tvText) {
        this.tvText = tvText;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Boolean doInBackground(Void... voids) {

        for (int i=1; i<=50; i++) {
            try {
                Thread.sleep(5);
            } catch (Exception e) {
                e.printStackTrace();
            }
            publishProgress(i);
        }

        return true;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);

        this.tvText.setText(Integer.toString(values[0]));

    }

    @Override
    protected void onPostExecute(Boolean aBoolean) {
        super.onPostExecute(aBoolean);
    }

    @Override
    protected void onCancelled(Boolean aBoolean) {
        super.onCancelled(aBoolean);
    }

}

 

 

 

 

 

 

 

 

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    TextView tvText;
    Button btnStart;

    MyAsyncTask myAsyncTask;

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

        tvText = findViewById(R.id.tvText);
        btnStart = findViewById(R.id.btnStart);

        myAsyncTask = new MyAsyncTask(tvText);

        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myAsyncTask.execute();
            }
        });

    }

}

실행 결과

 

 

한 번 더 클릭하면 에러 발생!

에러 발생

하나의 객체이므로 재사용 불가능.

execute() 한 번만 쓸 수 있음.

객체를 새로 생성해야 함.

 

(참고. Thread 객체도 start() 한 번만 사용 가능)

(그런 의미에서 Thread 객체랑 AsyncTask 객체랑 비슷하네)

---

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    TextView tvText;
    Button btnStart;

    MyAsyncTask myAsyncTask;

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

        tvText = findViewById(R.id.tvText);
        btnStart = findViewById(R.id.btnStart);

        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myAsyncTask = new MyAsyncTask(tvText);
                myAsyncTask.execute();
            }
        });

    }

}

실행 결과