深入淺析Android中DecorView與ViewRootImpl的區(qū)別

public void setContentView(@LayoutRes int layoutResID) {
   getWindow().setContentView(layoutResID); //調用getWindow方法，返回mWindow
   initWindowDecorActionBar();
}
...
public Window getWindow() {  
   return mWindow;
}

final void attach(Context context, ActivityThread aThread,
      Instrumentation instr, IBinder token, int ident,
      Application application, Intent intent, ActivityInfo info,
      CharSequence title, Activity parent, String id,
      NonConfigurationInstances lastNonConfigurationInstances,
      Configuration config, String referrer, IVoiceInteractor voiceInteractor) {
    ...
    mWindow = new PhoneWindow(this);
    ...
  }

@Override
public void setContentView(int layoutResID) {
  // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
  // decor, when theme attributes and the like are crystalized. Do not check the feature
  // before this happens.
  if (mContentParent == null) { // 1
    installDecor();
  } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
    mContentParent.removeAllViews();
  }

  if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
    final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
        getContext());
    transitionTo(newScene);
  } else {
    mLayoutInflater.inflate(layoutResID, mContentParent); // 2
  }
  final Callback cb = getCallback();
  if (cb != null && !isDestroyed()) {
    cb.onContentChanged();
  }
}

// This is the view in which the window contents are placed. It is either
// mDecor itself, or a child of mDecor where the contents go.
private ViewGroup mContentParent;

private void installDecor() {
  if (mDecor == null) {
    mDecor = generateDecor(); // 1
    mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
    mDecor.setIsRootNamespace(true);
    if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
      mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
    }
  }
  if (mContentParent == null) {
    mContentParent = generateLayout(mDecor); // 2
    ...
    } 
  }
}

protected DecorView generateDecor() {
  return new DecorView(getContext(), -1);
}

protected ViewGroup generateLayout(DecorView decor) {
    // Apply data from current theme.
    // 從主題文件中獲取樣式信息
    TypedArray a = getWindowStyle();

    ...

    if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) {
      requestFeature(FEATURE_NO_TITLE);
    } else if (a.getBoolean(R.styleable.Window_windowActionBar, false)) {
      // Don't allow an action bar if there is no title.
      requestFeature(FEATURE_ACTION_BAR);
    }

    if(...){
      ...
    }

    // Inflate the window decor.
    // 加載窗口布局
    int layoutResource;
    int features = getLocalFeatures();
    // System.out.println("Features: 0x" + Integer.toHexString(features));
    if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
      layoutResource = R.layout.screen_swipe_dismiss;
    } else if(...){
      ...
    }

    View in = mLayoutInflater.inflate(layoutResource, null);  //加載layoutResource
    decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); //往DecorView中添加子View，即mContentParent
    mContentRoot = (ViewGroup) in;

    ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT); // 這里獲取的就是mContentParent
    if (contentParent == null) {
      throw new RuntimeException("Window couldn't find content container view");
    }

    if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
      ProgressBar progress = getCircularProgressBar(false);
      if (progress != null) {
        progress.setIndeterminate(true);
      }
    }

    if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
      registerSwipeCallbacks();
    }

    // Remaining setup -- of background and title -- that only applies
    // to top-level windows.
    ...

    return contentParent;
  }

final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward) { 
  //...
  ActivityClientRecord r = performResumeActivity(token, clearHide); // 這里會調用到onResume()方法

  if (r != null) {
    final Activity a = r.activity;

    //...
    if (r.window == null && !a.mFinished && willBeVisible) {
      r.window = r.activity.getWindow(); // 獲得window對象
      View decor = r.window.getDecorView(); // 獲得DecorView對象
      decor.setVisibility(View.INVISIBLE);
      ViewManager wm = a.getWindowManager(); // 獲得windowManager對象
      WindowManager.LayoutParams l = r.window.getAttributes();
      a.mDecor = decor;
      l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
      l.softInputMode |= forwardBit;
      if (a.mVisibleFromClient) {
        a.mWindowAdded = true;
        wm.addView(decor, l); // 調用addView方法
      }
      //...
    }
  }
}

public final class WindowManagerImpl implements WindowManager {  
  private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
  ...
  @Override
  public void addView(View view, ViewGroup.LayoutParams params) {
    mGlobal.addView(view, params, mDisplay, mParentWindow);
  }
}

public void addView(View view, ViewGroup.LayoutParams params,
      Display display, Window parentWindow) {
    ...

    ViewRootImpl root;
    View panelParentView = null;

    synchronized (mLock) {
      ...

      root = new ViewRootImpl(view.getContext(), display); // 1

      view.setLayoutParams(wparams);

      mViews.add(view);
      mRoots.add(root);
      mParams.add(wparams);
    }

    // do this last because it fires off messages to start doing things
    try {
      root.setView(view, wparams, panelParentView); // 2
    } catch (RuntimeException e) {
      // BadTokenException or InvalidDisplayException, clean up.
      synchronized (mLock) {
        final int index = findViewLocked(view, false);
        if (index >= 0) {
          removeViewLocked(index, true);
        }
      }
      throw e;
    }
  }