Android implements the automatic update function of Android APP

// =======================================
// File: + MainActivity// (This example writes Manager and Activity in one place, and distinguishes it from comments)// =======================================
 
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// —— Play Core library dependencies (update now/flexible update)// implementation ":core:1.10.3"
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public class MainActivity extends AppCompatActivity {
 
    // ------------------------------------------------------------------------------------------------------------------------------    private static final int REQUEST_CODE_UPDATE = 100;               // Play update request code    private static final int REQUEST_INSTALL_PERMISSION = 101;        // Dynamic installation permissions    private static final String TAG = "AutoUpdate";
    private long downloadId;                                          // DownloadManager returns ID    private DownloadManager downloadManager;
 
    // ---------- onCreate ----------
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        (savedInstanceState);
        setContentView(.activity_main);  // See below for layout 
        // The button triggers two updates        Button btnPlayUpdate    = findViewById();
        Button btnCustomUpdate  = findViewById();
 
        (new () {
            @Override public void onClick(View v) {
                checkPlayUpdate();   // Play Store Update            }
        });
 
        (new () {
            @Override public void onClick(View v) {
                checkCustomUpdate(); // Self-built server update            }
        });
 
        // Initialize DownloadManager        downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
        // Register to download and complete the broadcast        registerReceiver(onDownloadComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
    }
 
    // --------- 1. Play In‑App Updates Check --------    private void checkPlayUpdate() {
        // Create AppUpdateManager         appUpdateManager =
                (this);
 
        // Get update information asynchronously        Task<AppUpdateInfo> appUpdateInfoTask = ();
        (info -> {
            // Determine whether there is an update and supports immediate update            if (() == UpdateAvailability.UPDATE_AVAILABLE
                    && ()) {
                try {
                    // Initiate a flexible update request                    (
                            info,
                            ,
                            this,
                            REQUEST_CODE_UPDATE);
                } catch (Exception e) {
                    (TAG, "Play update failed to start", e);
                }
            } else {
                (this, "No update available or this update type is not supported", Toast.LENGTH_SHORT).show();
            }
        });
    }
 
    // ---------- 2. Self-built server version detection ---------    private void checkCustomUpdate() {
        new Thread(() -> {
            try {
                // 1) Request server JSON                URL url = new URL("/latest_version.json");
                HttpURLConnection conn = (HttpURLConnection) ();
                (5000);
                ("GET");
                InputStream in = ();
                Scanner sc = new Scanner(in).useDelimiter("\\A");
                String json = () ? () : "";
                JSONObject obj = new JSONObject(json);
                final int serverVersionCode = ("versionCode");
                final String apkUrl       = ("apkUrl");
                final String changeLog   = ("changeLog");
 
                // 2) Get the local version number                int localVersionCode = getPackageManager()
                        .getPackageInfo(getPackageName(), 0).versionCode;
 
                if (serverVersionCode > localVersionCode) {
                    // There is a new version, go back to the main thread pop-up prompt                    runOnUiThread(() ->
                        showUpdateDialog(apkUrl, changeLog)
                    );
                } else {
                    runOnUiThread(() ->
                        (this, "It's the latest version", Toast.LENGTH_SHORT).show()
                    );
                }
            } catch (Exception e) {
                (TAG, "Check for update failed", e);
            }
        }).start();
    }
 
    // ---------- 3. An update dialog box pops up ---------    private void showUpdateDialog(String apkUrl, String changeLog) {
        new (this)
            .setTitle("Discover a new version")
            .setMessage(changeLog)
            .setCancelable(false)
            .setPositiveButton("Update now", (dialog, which) -> {
                startDownload(apkUrl);
            })
            .setNegativeButton("Let's talk about it later", null)
            .show();
    }
 
    // ---------- 4. Start the system DownloadManager Download APK ---------    private void startDownload(String apkUrl) {
         request = new ((apkUrl));
        (.NETWORK_WIFI
                                      | .NETWORK_MOBILE);
        ("Downloading update package");
        (Environment.DIRECTORY_DOWNLOADS, "");
        // Start downloading        downloadId = (request);
    }
 
    // ---------- 5. The monitoring download is completed and the installation is triggered.    private BroadcastReceiver onDownloadComplete = new BroadcastReceiver() {
        @Override public void onReceive(Context context, Intent intent) {
            long id = (DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            if (id != downloadId) return;
 
            // Download is completed, install the APK            File apkFile = new File((
                            Environment.DIRECTORY_DOWNLOADS), "");
 
            // Android 8.0+ requires request for installation of unknown application permissions            if (.SDK_INT >= Build.VERSION_CODES.O) {
                boolean canInstall = getPackageManager().canRequestPackageInstalls();
                if (!canInstall) {
                    // Request "install unknown application" permission                    (,
                        new String[]{.REQUEST_INSTALL_PACKAGES},
                        REQUEST_INSTALL_PERMISSION);
                    return;
                }
            }
            installApk(apkFile);
        }
    };
 
    // ---------- 6. Process the results of the application for permissions from unknown sources ---------    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        if (requestCode == REQUEST_INSTALL_PERMISSION) {
            if (>0 && grantResults[0]==PackageManager.PERMISSION_GRANTED) {
                // Trigger the installation again (assuming the APK is still downloading the directory)                File apkFile = new File((
                                Environment.DIRECTORY_DOWNLOADS), "");
                installApk(apkFile);
            } else {
                (this, "Installation permission denied, cannot be updated automatically", Toast.LENGTH_LONG).show();
            }
        }
        (requestCode, permissions, grantResults);
    }
 
    // ---------- 7. Install APK helper method --------    private void installApk(File apkFile) {
        Uri apkUri = (this,
                getPackageName() + ".fileprovider", apkFile);
 
        Intent intent = new Intent(Intent.ACTION_VIEW);
        (apkUri, "application/-archive");
        (Intent.FLAG_GRANT_READ_URI_PERMISSION);
        (Intent.FLAG_ACTIVITY_NEW_TASK);
        try {
            startActivity(intent);
        } catch (ActivityNotFoundException e) {
            (this, "Cannot start installer", Toast.LENGTH_LONG).show();
        }
    }
 
    // ---------- 8. Log out of Activity when destroyed Receiver --------    @Override
    protected void onDestroy() {
        ();
        unregisterReceiver(onDownloadComplete);
    }
}

<!-- ======================================
document: 
Notice：Requires configuration FileProvider With permissions
====================================== -->
<manifest xmlns:andro
    package="">
 
    <!-- Install unknown source permissions（Android 8.0+ Need to apply dynamically） -->
    <uses-permission android:name=".REQUEST_INSTALL_PACKAGES"/>
    <uses-permission android:name=""/>
    <uses-permission android:name=".WRITE_EXTERNAL_STORAGE"/>
 
    <application
        android:allowBackup="true"
        android:label="@string/app_name"
        android:theme="@style/">
 
        <!-- FileProvider statement -->
        <provider
            android:name=""
            android:authorities="${applicationId}.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name=".FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>
 
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name=""/>
                <category android:name=""/>
            </intent-filter>
        </activity>
    </application>
</manifest>

<!-- ======================================
document: res/xml/file_paths.xml
FileProvider Path configuration
====================================== -->
<paths xmlns:andro>
    <external-path name="download" path="Download/"/>
</paths>

<!-- ======================================
document: res/layout/activity_main.xml
Simple sample interface
====================================== -->
<LinearLayout xmlns:andro
    android:orientation="vertical" android:gravity="center"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:padding="24dp">
 
    <Button
        android:
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Play In‑App Update"/>
 
    <View android:layout_height="16dp" android:layout_width="match_parent"/>
 
    <Button
        android:
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Self-built service update"/>
</LinearLayout>