AsyncTask 사용법

* MainActivity.java

public class MainActivity extends AppCompatActivity {

    ProgressBar progressBar;

    int value;

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

        progressBar = findViewById(R.id.progressBar);

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                BackgroundTask task = new BackgroundTask();
                task.execute();
            }
        });
    }

    class BackgroundTask extends AsyncTask<Integer, Integer, Integer> {

        @Override
        protected void onPreExecute() {
            value = 0;
            progressBar.setProgress(value);
        }

        @Override
        protected void onPostExecute(Integer integer) {
            progressBar.setProgress(0);
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            progressBar.setProgress(values[0].intValue());
        }

        @Override
        protected Integer doInBackground(Integer... integers) {
            while (isCancelled() == false) {
                value++;

                if (value >= 100) {
                    break;
                }

                publishProgress(value);

                try {
                    Thread.sleep(1000);
                } catch (Exception e) {
                    //
                }
            }

            return value;
        }

    }

}

* activity_main.xml

public class MainActivity extends AppCompatActivity {

    ProgressBar progressBar;

    int value;

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

        progressBar = findViewById(R.id.progressBar);

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                BackgroundTask task = new BackgroundTask();
                task.execute();
            }
        });
    }

    class BackgroundTask extends AsyncTask<Integer, Integer, Integer> {

        @Override
        protected void onPreExecute() {
            value = 0;
            progressBar.setProgress(value);
        }

        @Override
        protected void onPostExecute(Integer integer) {
            progressBar.setProgress(0);
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            progressBar.setProgress(values[0].intValue());
        }

        @Override
        protected Integer doInBackground(Integer... integers) {
            while (isCancelled() == false) {
                value++;

                if (value >= 100) {
                    break;
                }

                publishProgress(value);

                try {
                    Thread.sleep(1000);
                } catch (Exception e) {
                    //
                }
            }

            return value;
        }

    }

}