RNThreadModule.java

package com.reactlibrary;

import android.os.Handler;
import android.os.Looper;
import android.util.Log;

import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactInstanceManager;
import com.facebook.react.ReactPackage;
import com.facebook.react.bridge.JSBundleLoader;
import com.facebook.react.bridge.LifecycleEventListener;
import com.facebook.react.bridge.Promise;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;
import com.facebook.react.devsupport.interfaces.DevSupportManager;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;


import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okio.Okio;
import okio.Sink;


public class RNThreadModule extends ReactContextBaseJavaModule implements LifecycleEventListener {

  private String TAG = "ThreadManager";
  private HashMap<Integer, JSThread> threads;

  private ReactApplicationContext reactApplicationContext;

  private ReactNativeHost reactNativeHost;

  private ReactPackage additionalThreadPackages[];

  public RNThreadModule(final ReactApplicationContext reactContext, ReactNativeHost reactNativehost, ReactPackage additionalThreadPackages[]) {
    super(reactContext);
    this.reactApplicationContext = reactContext;
    threads = new HashMap<>();
    this.reactNativeHost = reactNativehost;
    this.additionalThreadPackages = additionalThreadPackages;
    reactContext.addLifecycleEventListener(this);
  }

  @Override
  public String getName() {
    return "ThreadManager";
  }

  @ReactMethod
  public void startThread(final String jsFileName, final Promise promise) {
    Log.d(TAG, "Starting web thread - " + jsFileName);

    // When we create the absolute file path later, a "./" will break it.
    // Remove the leading "./" if it exists.
    String jsFileSlug = jsFileName.contains("./")
      ? jsFileName.replace("./", "")
      : jsFileName;

    JSBundleLoader bundleLoader = getDevSupportManager().getDevSupportEnabled()
            ? createDevBundleLoader(jsFileName, jsFileSlug)
            : createReleaseBundleLoader(jsFileName, jsFileSlug);

    try {
      ArrayList<ReactPackage> threadPackages = new ArrayList<ReactPackage>(Arrays.asList(additionalThreadPackages));
      threadPackages.add(0, new ThreadBaseReactPackage(getReactInstanceManager()));

      ReactContextBuilder threadContextBuilder = new ReactContextBuilder(getReactApplicationContext())
              .setJSBundleLoader(bundleLoader)
              .setDevSupportManager(getDevSupportManager())
              .setReactInstanceManager(getReactInstanceManager())
              .setReactPackages(threadPackages);

      JSThread thread = new JSThread(jsFileSlug);
      thread.runFromContext(
              getReactApplicationContext(),
              threadContextBuilder
      );
      threads.put(thread.getThreadId(), thread);
      promise.resolve(thread.getThreadId());
    } catch (Exception e) {
      promise.reject(e);
      getDevSupportManager().handleException(e);
    }
  }

  @ReactMethod
  public void stopThread(final int threadId) {
    final JSThread thread = threads.get(threadId);
    if (thread == null) {
      Log.d(TAG, "Cannot stop thread - thread is null for id " + threadId);
      return;
    }

    new Handler(Looper.getMainLooper()).post(new Runnable() {
      @Override
      public void run() {
        thread.terminate();
        threads.remove(threadId);
      }
    });
  }

  @ReactMethod
  public void postThreadMessage(int threadId, String message) {
    JSThread thread = threads.get(threadId);
    if (thread == null) {
      Log.d(TAG, "Cannot post message to thread - thread is null for id " + threadId);
      return;
    }

    thread.postMessage(message);
  }

  @Override
  public void onHostResume() {
    new Handler(Looper.getMainLooper()).post(new Runnable() {
      @Override
      public void run() {
        for (int threadId : threads.keySet()) {
          threads.get(threadId).onHostResume();
        }
      }
    });
  }

  @Override
  public void onHostPause() {
    new Handler(Looper.getMainLooper()).post(new Runnable() {
      @Override
      public void run() {
        for (int threadId : threads.keySet()) {
          threads.get(threadId).onHostPause();
        }
      }
    });
  }

  @Override
  public void onHostDestroy() {
    Log.d(TAG, "onHostDestroy - Clean JS Threads");

    new Handler(Looper.getMainLooper()).post(new Runnable() {
      @Override
      public void run() {
        for (int threadId : threads.keySet()) {
          threads.get(threadId).terminate();
        }
      }
    });
  }

  @Override
  public void onCatalystInstanceDestroy() {
    super.onCatalystInstanceDestroy();
    onHostDestroy();
  }

    /*
     *  Helper methods
     */

  private JSBundleLoader createDevBundleLoader(String jsFileName, String jsFileSlug) {
    String bundleUrl = bundleUrlForFile(jsFileName);
    // nested file directory will not exist in the files dir during development,
    // so remove any leading directory paths to simply download a flat file into
    // the root of the files directory.
    String[] splitFileSlug = jsFileSlug.split("/");
    String bundleOut = getReactApplicationContext().getFilesDir().getAbsolutePath() + "/" + splitFileSlug[splitFileSlug.length - 1];

    Log.d(TAG, "createDevBundleLoader - download web thread to - " + bundleOut);
    downloadScriptToFileSync(bundleUrl, bundleOut);

    return JSBundleLoader.createCachedBundleFromNetworkLoader(bundleUrl, bundleOut);
  }

  private JSBundleLoader createReleaseBundleLoader(String jsFileName, String jsFileSlug) {
    Log.d(TAG, "createReleaseBundleLoader - reading file from assets");
    return JSBundleLoader.createAssetLoader(reactApplicationContext, "assets://threads/" + jsFileSlug + ".bundle", false);
  }

  private ReactInstanceManager getReactInstanceManager() {
    return reactNativeHost.getReactInstanceManager();
  }

  private DevSupportManager getDevSupportManager() {
    return getReactInstanceManager().getDevSupportManager();
  }

  private String bundleUrlForFile(final String fileName) {
    // http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false
    String sourceUrl = getDevSupportManager().getSourceUrl().replace("http://", "");
    return  "http://"
            + sourceUrl.split("/")[0]
            + "/"
            + fileName
            + ".bundle?platform=android&dev=true&hot=false&minify=false";
  }

  private void downloadScriptToFileSync(String bundleUrl, String bundleOut) {
    OkHttpClient client = new OkHttpClient();
    final File out = new File(bundleOut);

    Request request = new Request.Builder()
            .url(bundleUrl)
            .build();

    try {
      Response response = client.newCall(request).execute();
      if (!response.isSuccessful()) {
        throw new RuntimeException("Error downloading thread script - " + response.toString());
      }

      Sink output = Okio.sink(out);
      Okio.buffer(response.body().source()).readAll(output);
    } catch (IOException e) {
      throw new RuntimeException("Exception downloading thread script to file", e);
    }
  }
}