Android 插件化處理方案詳解

更新時間：2021年04月06日 08:32:39 作者：bobby_developer

這篇文章主要介紹了Android 插件化處理方案的相關資料，幫助大家更好的理解和學習使用Android開發(fā)，感興趣的朋友可以了解下

插件化啟動Activity的過程

在宿主里面的AndroidManifest.xml里面注冊一個空的activity

從開始執(zhí)行execStartActivity到最終將Activity對象new出來這個過程，系統(tǒng)層會去校驗需要啟動的activity的合法性[就是是否有在某個應用的AndroidManifest.xml里面注冊]以及按啟動要求創(chuàng)建activity對象。清晰了這點我們就可以很好的繞過系統(tǒng)的約束，達到我們的目的：【插件中的組件擁有真正生命周期，完全交由系統(tǒng)管理、非反射代理】。簡單來說方案就兩步： Step1、在開始startActivity的時候將需要啟動的插件組件替換成宿主預先聲明號的。

public ActivityResult execStartActivity(Context who, IBinder contextThread, IBinder token, Activity target,
                    Intent intent, int requestCode, Bundle options) {

  //如果啟動的是插件的activity組件，這里面將會被替換成宿主預先聲明的
  PluginIntentResolver.resolveActivity(intent);
  return hackInstrumentation.execStartActivity(who, contextThread, token, target, intent, requestCode, ptions);
}

Step2、在最終創(chuàng)建activity對象的時候改回成插件組件的。

@Override
public Activity newActivity(ClassLoader cl, String className, Intent intent) throws InstantiationException,
    IllegalAccessException, ClassNotFoundException {

  ClassLoader orignalCl = cl;
  String orginalClassName = className;
  String orignalIntent = intent.toString();
  if (ProcessUtil.isPluginProcess()) {
    // 將PluginStubActivity替換成插件中的activity
    if (PluginManagerHelper.isStub(className)) {
      String action = intent.getAction();
      if (action != null && action.contains(PluginIntentResolver.CLASS_SEPARATOR)) {
        String[] targetClassName = action.split(PluginIntentResolver.CLASS_SEPARATOR);
        String pluginClassName = targetClassName[0];
        final String pid = intent.getStringExtra(PluginIntentResolver.INTENT_EXTRA_PID).trim();
        PluginDescriptor pluginDescriptor = TextUtils.isEmpty(pid) ? PluginManagerHelper.getPluginDescriptorByClassName(pluginClassName) : PluginManagerHelper.getPluginDescriptorByPluginId(pid);
        Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, pluginClassName);
        if (clazz != null) {
          className = pluginClassName;
          cl = clazz.getClassLoader();
          intent.setExtrasClassLoader(cl);
          if (targetClassName.length > 1) {
            // 之前為了傳遞classNae，intent的action被修改過
            // 這里再把Action還原到原始的Action
            intent.setAction(targetClassName[1]);
          } else {
            intent.setAction(null);
          }
          // 添加一個標記符
          intent.addCategory(RELAUNCH_FLAG + className);
        } else {
          throw new ClassNotFoundException("pluginClassName : " + pluginClassName, new Throwable());
        }
      } else if (PluginManagerHelper.isExact(className, PluginDescriptor.ACTIVITY)) {
        // 這個邏輯是為了支持外部app喚起配置了stub_exact的插件Activity
        PluginDescriptor pluginDescriptor = PluginManagerHelper.getPluginDescriptorByClassName(className);
        if (pluginDescriptor != null) {
          boolean isRunning = PluginLauncher.instance().isRunning(pluginDescriptor.getPackageName());
          if (!isRunning) {
            return waitForLoading(pluginDescriptor);
          }
        }
        Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, className);
        if (clazz != null) {
          cl = clazz.getClassLoader();
        } else {
          throw new ClassNotFoundException("className : " + className, new Throwable());
        }
      } else {
        // 進入這個分支可能是因為activity重啟了，比如橫豎屏切換，由于上面的分支已經把Action還原到原始到Action了
        // 這里只能通過之前添加的標記符來查找className
        boolean found = false;
        Set<String> category = intent.getCategories();
        if (category != null) {
          Iterator<String> itr = category.iterator();
          while (itr.hasNext()) {
            String cate = itr.next();
            if (cate.startsWith(RELAUNCH_FLAG)) {
              className = cate.replace(RELAUNCH_FLAG, "");
              PluginDescriptor pluginDescriptor = PluginManagerHelper.getPluginDescriptorByClassName(className);
              if (pluginDescriptor != null) {
                boolean isRunning = PluginLauncher.instance().isRunning(
                    pluginDescriptor.getPackageName());
                if (!isRunning) {
                  return waitForLoading(pluginDescriptor);
                }
              }
              Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, className);
              cl = clazz.getClassLoader();
              found = true;
              break;
            }
          }
        }
        if (!found) {
          throw new ClassNotFoundException(
              "className : " + className + ", intent : " + intent.toString(), new Throwable());
        }
      }
    } else {
      if (cl instanceof PluginClassLoader) {
        PluginIntentResolver.resolveActivity(intent);
      } else {
        // Do Nothing
      }
    }
  }
  try {
    Activity activity = super.newActivity(cl, className, intent);
    if (activity instanceof PluginContainer) {
      ((PluginContainer) activity).setPluginId(intent.getStringExtra(PluginContainer.FRAGMENT_PLUGIN_ID));
    }
    return activity;
  } catch (ClassNotFoundException e) {
    // 收集狀態(tài)，便于異常分析
    throw new ClassNotFoundException(" orignalCl : " + orignalCl.toString() + ", orginalClassName : "
        + orginalClassName + ", orignalIntent : " + orignalIntent + ", currentCl : " + cl.toString()
        + ", currentClassName : " + className + ", currentIntent : " + intent.toString() + ", process : "
        + ProcessUtil.isPluginProcess() + ", isStubActivity : "
        + PluginManagerHelper.isStub(orginalClassName) + ", isExact : "
        + PluginManagerHelper.isExact(orginalClassName, PluginDescriptor.ACTIVITY), e);
  }
}

方案確實很簡單，不過還有一些收尾工作，就是將創(chuàng)建好的[插件]組件進行一些必要的init操作，比如：在聲明周期onCreate之前進行上下文替換等操作，這些都在插件框架提供的PluginInstrumentionWrapper里面進行完成的，看一下代碼片段：

@Override
public void callActivityOnCreate(Activity activity, Bundle icicle) {
  PluginInjector.injectActivityContext(activity);

  Intent intent = activity.getIntent();

  if (intent != null) {
    intent.setExtrasClassLoader(activity.getClassLoader());
  }
  if (icicle != null) {
    icicle.setClassLoader(activity.getClassLoader());
  }
  if (ProcessUtil.isPluginProcess()) {
    installPluginViewFactory(activity);
    if (activity instanceof WaitForLoadingPluginActivity) {
      // NOTHING
    } else {
    }
    if (activity.isChild()) {
      // 修正TabActivity中的Activity的ContextImpl的packageName
      Context base = activity.getBaseContext();
      while (base instanceof ContextWrapper) {
        base = ((ContextWrapper) base).getBaseContext();
      }
      if (HackContextImpl.instanceOf(base)) {
        HackContextImpl impl = new HackContextImpl(base);
        String packageName = PluginLoader.getApplication().getPackageName();
        // String packageName1 = activity.getPackageName();
        impl.setBasePackageName(packageName);
        impl.setOpPackageName(packageName);
      }
    }
  }
  super.callActivityOnCreate(activity, icicle);
  monitor.onActivityCreate(activity);
}

到這插件activity組件就被順序的啟動起來了，并且是系統(tǒng)在維護具備完整的生命周期。組件service、Receiver也是一樣的，只是這兩個組件的攔截點在ActivityThread的Handler成員的回調Callback里面進行的。Application和provider在插件啟動的時候進行加載。