Die Anleitung zu Android AsyncTask

<?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">

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView_info"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:gravity="center"
        android:text="Working info"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/progressBar" />

    <Button
        android:id="@+id/button_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Click to Start"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_info" />

    <Button
        android:id="@+id/button_cancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="Cancel"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_start" />

</androidx.constraintlayout.widget.ConstraintLayout>

package org.o7planning.asynctaskexample;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private ProgressBar progressBar;
    private TextView textViewInfo;
    private Button buttonStart;
    private Button buttonCancel;

    private MyWorkTask myWorkTask;

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

        this.progressBar = (ProgressBar) this.findViewById(R.id.progressBar);
        this.textViewInfo = (TextView) this.findViewById(R.id.textView_info);
        this.buttonStart = (Button) this.findViewById(R.id.button_start);
        this.buttonCancel = (Button) this.findViewById(R.id.button_cancel);

        this.buttonStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startWork();
            }
        });
        this.buttonCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                requestCancel();
            }
        });
    }

    private void startWork()  {
        this.myWorkTask = new MyWorkTask(this.progressBar,
                this.textViewInfo, this.buttonStart, this.buttonCancel);

        ParamInfo param = new ParamInfo("Param 1", "Param 2");

        this.myWorkTask.execute(param);
    }

    private void requestCancel()  {
        if(this.myWorkTask != null)  {
            this.myWorkTask.cancel(true);
        }
    }
}

package org.o7planning.asynctaskexample;

import android.os.AsyncTask;
import android.os.SystemClock;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.util.Date;

// <Params, Progress, Result>
public class MyWorkTask extends AsyncTask<ParamInfo, ProgressInfo, ResultInfo> {

    private final ProgressBar progressBar;
    private final TextView textViewInfo;
    private final Button buttonStart;
    private final Button buttonCancel;

    private final int PROGRESS_MAX;
    private int workCount = 0;
    private long startTimeInMillis;

    public MyWorkTask(ProgressBar progressBar, TextView textViewInfo,
                      Button buttonStart, Button buttonCancel)  {
        this.progressBar = progressBar;
        this.textViewInfo = textViewInfo;
        this.buttonStart = buttonStart;
        this.buttonCancel = buttonCancel;
        this.PROGRESS_MAX = this.progressBar.getMax();
    }

    @Override
    protected void onPreExecute() {
        this.progressBar.setVisibility(ProgressBar.VISIBLE);
        this.textViewInfo.setText("Start...");
        this.buttonStart.setEnabled(false);
        this.buttonCancel.setEnabled(true);
        this.startTimeInMillis = new Date().getTime();
    }

    @Override
    protected ResultInfo doInBackground(ParamInfo... params) {
        final int WORK_MAX = 30;

        while (this.workCount < WORK_MAX) {
            SystemClock.sleep(100); // 100 Milliseconds.
            this.workCount++;

            int progress = (this.workCount * PROGRESS_MAX) / WORK_MAX; // Progress value.
            int percent = (progress * 100) / PROGRESS_MAX;
            String info = "(" + percent +"%) - Working part " + this.workCount + " of " + WORK_MAX;

            ProgressInfo progressInfo = new ProgressInfo(progress, info);
            this.publishProgress(progressInfo); // Progress ...values
        }
        long finishTimeInMillis = new Date().getTime();
        long workTimeInMillis = finishTimeInMillis - this.startTimeInMillis;
        ResultInfo result = new ResultInfo(true, workTimeInMillis);
        return result;
    }

    @Override
    protected void onProgressUpdate(ProgressInfo... values) { // Progress ...values
        ProgressInfo progressInfo= values[0];

        int progress = progressInfo.getProgress();

        this.progressBar.setProgress(progress);
        this.textViewInfo.setText(progressInfo.getWorkingInfo());
    }

    @Override
    protected void onPostExecute(ResultInfo resultInfo) {
        super.onPostExecute(resultInfo);
        this.buttonStart.setEnabled(true);
        this.buttonCancel.setEnabled(false);
        this.textViewInfo.setText(resultInfo.getMessage());
    }

    @Override
    protected void onCancelled(ResultInfo resultInfo) {
        super.onCancelled(resultInfo);
        this.buttonStart.setEnabled(true);
        this.buttonCancel.setEnabled(false);
        this.textViewInfo.setText(resultInfo.getMessage());
    }
}

package org.o7planning.asynctaskexample;

public class ParamInfo {
    private String param1;
    private String param2;

    public ParamInfo(String param1, String param2)  {
        this.param1 = param1;
        this.param2 = param2;
    }

    public String getParam1() {
        return param1;
    }

    public String getParam2() {
        return param2;
    }
}

package org.o7planning.asynctaskexample;

public class ProgressInfo {
    private int progress;
    private String workingInfo;

    public ProgressInfo(int progress, String workingInfo) {
        this.progress = progress;
        this.workingInfo = workingInfo;
    }
    public int getProgress() {
        return progress;
    }

    public String getWorkingInfo() {
        return workingInfo;
    }
}

package org.o7planning.asynctaskexample;

public class ResultInfo {
    private boolean completed;
    private long workTimeInMillis;

    public ResultInfo(boolean completed, long workTimeInMillis) {
        this.completed = completed;
        this.workTimeInMillis = workTimeInMillis;
    }

    public boolean isCompleted() {
        return completed;
    }

    public long getWorkTimeInMillis() {
        return workTimeInMillis;
    }

    public String getMessage() {
        if(this.completed)  {
            return "Complete in " + this.workTimeInMillis +" milliseconds";
        }
        return "Failed or cancelled";
    }
}