Android 응용프로그램 레이어 View 드로잉 프로세스의 DecorView 및 ViewRootImpl

public void setContentView(@LayoutRes int layoutResID) {
     getWindow().setContentView(layoutResID);
     initWindowDecorActionBar();
 }

 public void setContentView(View view) {
       getWindow().setContentView(view);
       initWindowDecorActionBar();
   }

public void setContentView(View view, ViewGroup.LayoutParams params) {
       getWindow().setContentView(view, params);
       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,
           Window window) {
       attachBaseContext(context);

       mFragments.attachHost(null /*parent*/);

       mWindow = new PhoneWindow(this, window);
       mWindow.setWindowControllerCallback(this);
       mWindow.setCallback(this);
       mWindow.setOnWindowDismissedCallback(this);
       mWindow.getLayoutInflater().setPrivateFactory(this);
       ..........
       ..........
   }

/**
 * Abstract base class for a top-level window look and behavior policy.  An
 * instance of this class should be used as the top-level view added to the
 * window manager. It provides standard UI policies such as a background, title
 * area, default key processing, etc.
 *
 * 
The only existing implementation of this abstract class is
 * android.view.PhoneWindow, which you should instantiate when needing a
 * Window.
 */
public abstract class Window {

 @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) {
        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);
    }
    mContentParent.requestApplyInsets();
    final Callback cb = getCallback();
    if (cb != null && !isDestroyed()) {
        cb.onContentChanged();
    }
    mContentParentExplicitlySet = true;
}

@Override
public void setContentView(View view) {
    setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
}

@Override
public void setContentView(View view, ViewGroup.LayoutParams params) {
    // 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) {
        installDecor();
    } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
        mContentParent.removeAllViews();
    }
    if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
        view.setLayoutParams(params);
        final Scene newScene = new Scene(mContentParent, view);
        transitionTo(newScene);
    } else {
        mContentParent.addView(view, params);
    }
    mContentParent.requestApplyInsets();
    final Callback cb = getCallback();
    if (cb != null && !isDestroyed()) {
        cb.onContentChanged();
    }
    mContentParentExplicitlySet = true;
}

 private void installDecor() {
        mForceDecorInstall = false;
        if (mDecor == null) {
            mDecor = generateDecor(-1);
            mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
            mDecor.setIsRootNamespace(true);
            if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
                mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
            }
        } else {
            mDecor.setWindow(this);
        }
        if (mContentParent == null) {
            mContentParent = generateLayout(mDecor);
        ........
        .......
}

ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
  if (contentParent == null) {
      throw new RuntimeException("Window couldn't find content container view");
  }
....
return contentParent;

  /**
    * The ID that the main layout in the XML layout file should have.
    */
   public static final int ID_ANDROID_CONTENT = com.android.internal.R.id.content;

     mContentParent.addView(view, params);

/**
    * Adds a child view with the specified layout parameters.
    *
    * 
Note: do not invoke this method from
    * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
    * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.
    *
    * @param child the child view to add
    * @param index the position at which to add the child or -1 to add last
    * @param params the layout parameters to set on the child
    */
   public void addView(View child, int index, LayoutParams params) {
       if (DBG) {
           System.out.println(this + " addView");
       }

       if (child == null) {
           throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
       }

       // addViewInner() will call child.requestLayout() when setting the new LayoutParams
       // therefore, we call requestLayout() on ourselves before, so that the child's request
       // will be blocked at our level
       requestLayout();
       invalidate(true);
       addViewInner(child, index, params, false);
   }

final void handleResumeActivity(IBinder token,
        boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) {
    ActivityClientRecord r = mActivities.get(token);
    if (!checkAndUpdateLifecycleSeq(seq, r, "resumeActivity")) {
        return;
    }

    // If we are getting ready to gc after going to the background, well
    // we are back active so skip it.
    unscheduleGcIdler();
    mSomeActivitiesChanged = true;

    // TODO Push resumeArgs into the activity for consideration
    r = performResumeActivity(token, clearHide, reason);

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

        if (localLOGV) Slog.v(
            TAG, "Resume " + r + " started activity: " +
            a.mStartedActivity + ", hideForNow: " + r.hideForNow
            + ", finished: " + a.mFinished);

        final int forwardBit = isForward ?
                WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;

        // If the window hasn't yet been added to the window manager,
        // and this guy didn't finish itself or start another activity,
        // then go ahead and add the window.
        boolean willBeVisible = !a.mStartedActivity;
        if (!willBeVisible) {
            try {
                willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(
                        a.getActivityToken());
            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }
        }
        if (r.window == null && !a.mFinished && willBeVisible) {
            r.window = r.activity.getWindow();
            View decor = r.window.getDecorView();
            decor.setVisibility(View.INVISIBLE);
            ViewManager wm = a.getWindowManager();
            WindowManager.LayoutParams l = r.window.getAttributes();
            a.mDecor = decor;
            l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
            l.softInputMode |= forwardBit;
            if (r.mPreserveWindow) {
                a.mWindowAdded = true;
                r.mPreserveWindow = false;
                // Normally the ViewRoot sets up callbacks with the Activity
                // in addView->ViewRootImpl#setView. If we are instead reusing
                // the decor view we have to notify the view root that the
                // callbacks may have changed.
                ViewRootImpl impl = decor.getViewRootImpl();
                if (impl != null) {
                    impl.notifyChildRebuilt();
                }
            }
            if (a.mVisibleFromClient && !a.mWindowAdded) {
                a.mWindowAdded = true;
                wm.addView(decor, l);
            }

        ................................
    }
}

      public interface WindowManager extends ViewManager {

/** Interface to let you add and remove child views to an Activity. To get an instance
  * of this class, call {@link android.content.Context#getSystemService(java.lang.String) Context.getSystemService()}.
  */
public interface ViewManager
{
    /**
     * Assign the passed LayoutParams to the passed View and add the view to the window.
     * 
Throws {@link android.view.WindowManager.BadTokenException} for certain programming
     * errors, such as adding a second view to a window without removing the first view.
     * 
Throws {@link android.view.WindowManager.InvalidDisplayException} if the window is on a
     * secondary {@link Display} and the specified display can't be found
     * (see {@link android.app.Presentation}).
     * @param view The view to be added to this window.
     * @param params The LayoutParams to assign to view.
     */
    public void addView(View view, ViewGroup.LayoutParams params);
    public void updateViewLayout(View view, ViewGroup.LayoutParams params);
    public void removeView(View view);
}

@Override
   public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
       applyDefaultToken(params);
       mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
   }

public void addView(View view, ViewGroup.LayoutParams params,
           Display display, Window parentWindow) {
       ........................
       ViewRootImpl root;
       View panelParentView = null;

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

           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);
       } catch (RuntimeException e) {
           // BadTokenException or InvalidDisplayException, clean up.
           synchronized (mLock) {
               final int index = findViewLocked(view, false);
               if (index >= 0) {
                   removeViewLocked(index, true);
               }
           }
           throw e;
       }
   }

// Schedule the first layout -before- adding to the window
// manager, to make sure we do the relayout before receiving
// any other events from the system.
requestLayout();

    @Override
    public void requestLayout() {
        if (!mHandlingLayoutInLayoutRequest) {
            checkThread();
            mLayoutRequested = true;
            scheduleTraversals();
        }
    }

void scheduleTraversals() {
       if (!mTraversalScheduled) {
           mTraversalScheduled = true;
           mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
           mChoreographer.postCallback(
                   Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
           if (!mUnbufferedInputDispatch) {
               scheduleConsumeBatchedInput();
           }
           notifyRendererOfFramePending();
           pokeDrawLockIfNeeded();
       }
   }

final class TraversalRunnable implements Runnable {
       @Override
       public void run() {
           doTraversal();
       }
   }
   final TraversalRunnable mTraversalRunnable = new TraversalRunnable();

void doTraversal() {
       if (mTraversalScheduled) {
           mTraversalScheduled = false;
           mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);

           if (mProfile) {
               Debug.startMethodTracing("ViewAncestor");
           }

           performTraversals();

           if (mProfile) {
               Debug.stopMethodTracing();
               mProfile = false;
           }
       }
   }

private void performTraversals() {
        ......
        int childWidthMeasureSpec = getRootMeasureSpec(mWidth, lp.width);
        int childHeightMeasureSpec = getRootMeasureSpec(mHeight, lp.height);
        ......
        mView.measure(childWidthMeasureSpec, childHeightMeasureSpec);
        ......
        mView.layout(0, 0, mView.getMeasuredWidth(), mView.getMeasuredHeight());
        ......
        mView.draw(canvas);
        ......
    }