live data android example

different files

/* вместо AsyncTask был использован Thread для выполнения операций в фоновом режиме в MainViewModel.
также, для обновления UI с использованием LiveData, был использован Handler для отправки сообщений в основной поток */

MainActivity.java:

package com.sunmeat.async;

import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.ViewModelProvider;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;
    private ProgressBar progressBar;
    private MainViewModel viewModel;

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

        Button button = findViewById(R.id.btnProgressBar);
        imageView = findViewById(R.id.my_image);
        progressBar = findViewById(R.id.progressBar);

        viewModel = new ViewModelProvider(this, ViewModelProvider.AndroidViewModelFactory.getInstance(getApplication())).get(MainViewModel.class);

        viewModel.getProgressLiveData().observe(this, progress -> {
            progressBar.setProgress(progress);
        });

        viewModel.getImagePathLiveData().observe(this, imagePath -> {
            imageView.setImageDrawable(Drawable.createFromPath(imagePath));
        });

        button.setOnClickListener(v -> viewModel.downloadFile(this));
    }
}

===================================================================================================================

MainViewModel.java:

package com.sunmeat.async;

import android.content.Context;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
import java.io.BufferedInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;
import java.nio.file.Paths;

public class MainViewModel extends ViewModel {

    private final MutableLiveData<Integer> progressLiveData = new MutableLiveData<>();
    private final MutableLiveData<String> imagePathLiveData = new MutableLiveData<>();

    LiveData<Integer> getProgressLiveData() {
        return progressLiveData;
    }

    LiveData<String> getImagePathLiveData() {
        return imagePathLiveData;
    }

    void downloadFile(Context context) {
        new Thread(() -> {
            try {
                String fileUrl = "https://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Mona_Lisa%2C_by_Leonardo_da_Vinci%2C_from_C2RMF_retouched.jpg/375px-Mona_Lisa%2C_by_Leonardo_da_Vinci%2C_from_C2RMF_retouched.jpg";
                URL url = new URL(fileUrl);
                URLConnection connection = url.openConnection();
                connection.connect();

                int lengthOfFile = connection.getContentLength();

                InputStream input = new BufferedInputStream(url.openStream(), 8192);

                OutputStream output = Files.newOutputStream(Paths.get(context.getFilesDir() + "/downloadedfile.jpg"));

                byte data[] = new byte[1024];

                long total = 0;

                int count;
                while ((count = input.read(data)) != -1) {
                    total += count;
                    int progress = (int) (total * 100 / lengthOfFile);
                    progressLiveData.postValue(progress);
                    output.write(data, 0, count);
                }

                output.flush();
                output.close();
                input.close();

                String imagePath = context.getFilesDir() + "/downloadedfile.jpg";
                imagePathLiveData.postValue(imagePath);

            } catch (Exception e) {
                e.printStackTrace();
            }
        }).start();
    }
}

===================================================================================================================

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btnProgressBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="Download Image" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"

        android:layout_height="wrap_content"
        android:layout_margin="10dp" />

    <ImageView
        android:id="@+id/my_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="10dp" />

</LinearLayout>

===================================================================================================================

AndroidManifest.xml:

...
<uses-permission android:name="android.permission.INTERNET" />
...

===================================================================================================================

build.gradle.kts (Module:app):

dependencies {
 ...
    implementation ("android.arch.lifecycle:extensions:1.1.1")
    annotationProcessor ("android.arch.lifecycle:compiler:1.1.1")
    implementation ("androidx.lifecycle:lifecycle-viewmodel:2.7.0")
    implementation ("androidx.lifecycle:lifecycle-livedata:2.7.0")
    implementation ("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.1")
}