Extract async processor interface

On the server side, several components are started, stopped and joined.
Extract an interface to handle them generically.

This will help to support both encoded and raw audio stream, because
they will be two different concrete components, but implementing the
same interface.

PR #3757 <https://github.com/Genymobile/scrcpy/pull/3757>

server/src/main/java/com/genymobile/scrcpy/AsyncProcessor.java

@@ -0,0 +1,7 @@
+package com.genymobile.scrcpy;
+
+public interface AsyncProcessor {
+    void start();
+    void stop();
+    void join() throws InterruptedException;
+}

server/src/main/java/com/genymobile/scrcpy/AudioEncoder.java

@@ -14,7 +14,7 @@ import java.util.List;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
 
-public final class AudioEncoder {
+public final class AudioEncoder implements AsyncProcessor {
 
     private static class InputTask {
         private final int index;

server/src/main/java/com/genymobile/scrcpy/Controller.java

@@ -14,7 +14,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
-public class Controller {
+public class Controller implements AsyncProcessor {
 
     private static final int DEFAULT_DEVICE_ID = 0;
 

server/src/main/java/com/genymobile/scrcpy/Server.java

@@ -5,6 +5,7 @@ import android.os.BatteryManager;
 import android.os.Build;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 
@@ -91,8 +92,7 @@ public final class Server {
             Workarounds.fillAppInfo();
         }
 
-        Controller controller = null;
-        AudioEncoder audioEncoder = null;
+        List<AsyncProcessor> asyncProcessors = new ArrayList<>();
 
         try (DesktopConnection connection = DesktopConnection.open(scid, tunnelForward, audio, control, sendDummyByte)) {
             if (options.getSendDeviceMeta()) {
@@ -101,24 +101,27 @@ public final class Server {
             }
 
             if (control) {
-                controller = new Controller(device, connection, options.getClipboardAutosync(), options.getPowerOn());
-                controller.start();
-
-                final Controller controllerRef = controller;
-                device.setClipboardListener(text -> controllerRef.getSender().pushClipboardText(text));
+                Controller controller = new Controller(device, connection, options.getClipboardAutosync(), options.getPowerOn());
+                device.setClipboardListener(text -> controller.getSender().pushClipboardText(text));
+                asyncProcessors.add(controller);
             }
 
             if (audio) {
                 Streamer audioStreamer = new Streamer(connection.getAudioFd(), options.getAudioCodec(), options.getSendCodecId(),
                         options.getSendFrameMeta());
-                audioEncoder = new AudioEncoder(audioStreamer, options.getAudioBitRate(), options.getAudioCodecOptions(), options.getAudioEncoder());
-                audioEncoder.start();
+                AudioEncoder audioRecorder = new AudioEncoder(audioStreamer, options.getAudioBitRate(), options.getAudioCodecOptions(), options.getAudioEncoder());
+                asyncProcessors.add(audioRecorder);
             }
 
             Streamer videoStreamer = new Streamer(connection.getVideoFd(), options.getVideoCodec(), options.getSendCodecId(),
                     options.getSendFrameMeta());
             ScreenEncoder screenEncoder = new ScreenEncoder(device, videoStreamer, options.getVideoBitRate(), options.getMaxFps(),
                     options.getVideoCodecOptions(), options.getVideoEncoder(), options.getDownsizeOnError());
+
+            for (AsyncProcessor asyncProcessor : asyncProcessors) {
+                asyncProcessor.start();
+            }
+
             try {
                 // synchronous
                 screenEncoder.streamScreen();
@@ -131,20 +134,14 @@ public final class Server {
         } finally {
             Ln.d("Screen streaming stopped");
             initThread.interrupt();
-            if (audioEncoder != null) {
-                audioEncoder.stop();
-            }
-            if (controller != null) {
-                controller.stop();
+            for (AsyncProcessor asyncProcessor : asyncProcessors) {
+                asyncProcessor.stop();
             }
 
             try {
                 initThread.join();
-                if (audioEncoder != null) {
-                    audioEncoder.join();
-                }
-                if (controller != null) {
-                    controller.join();
+                for (AsyncProcessor asyncProcessor : asyncProcessors) {
+                    asyncProcessor.join();
                 }
             } catch (InterruptedException e) {
                 // ignore