Android源码解读-View绘制流程之setContentView

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

PhoneWindow.java
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.
    //-------------------------------------1
    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 {
    //------------------------------------2
        mLayoutInflater.inflate(layoutResID, mContentParent);
    }
    mContentParent.requestApplyInsets();
    final Callback cb = getCallback();
    if (cb != null && !isDestroyed()) {
        cb.onContentChanged();
    }
    mContentParentExplicitlySet = true;
}

LayoutInflater.java
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
    synchronized (mConstructorArgs) {
        Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate");

        final Context inflaterContext = mContext;
        final AttributeSet attrs = Xml.asAttributeSet(parser);
        Context lastContext = (Context) mConstructorArgs[0];
        mConstructorArgs[0] = inflaterContext;
        View result = root;

        try {
            advanceToRootNode(parser);
            final String name = parser.getName();

            if (DEBUG) {
                System.out.println("**************************");
                System.out.println("Creating root view: "
                        + name);
                System.out.println("**************************");
            }

            if (TAG_MERGE.equals(name)) {
                if (root == null || !attachToRoot) {
                    throw new InflateException("<merge /> can be used only with a valid "
                            + "ViewGroup root and attachToRoot=true");
                }

                rInflate(parser, root, inflaterContext, attrs, false);
            } else {
                // Temp is the root view that was found in the xml
                final View temp = createViewFromTag(root, name, inflaterContext, attrs);

                ViewGroup.LayoutParams params = null;

                if (root != null) {
                    if (DEBUG) {
                        System.out.println("Creating params from root: " +
                                root);
                    }
                    // Create layout params that match root, if supplied
                    params = root.generateLayoutParams(attrs);
                    if (!attachToRoot) {
                        // Set the layout params for temp if we are not
                        // attaching. (If we are, we use addView, below)
                        temp.setLayoutParams(params);
                    }
                }

                if (DEBUG) {
                    System.out.println("-----> start inflating children");
                }

                // Inflate all children under temp against its context.
                //----------------------------------------------------1
                rInflateChildren(parser, temp, attrs, true);

                if (DEBUG) {
                    System.out.println("-----> done inflating children");
                }

                // We are supposed to attach all the views we found (int temp)
                // to root. Do that now.
                //----------------------------------------------------2
                if (root != null && attachToRoot) {
                    root.addView(temp, params);
                }

                // Decide whether to return the root that was passed in or the
                // top view found in xml.
                if (root == null || !attachToRoot) {
                    result = temp;
                }
            }

        } catch (XmlPullParserException e) {
            final InflateException ie = new InflateException(e.getMessage(), e);
            ie.setStackTrace(EMPTY_STACK_TRACE);
            throw ie;
        } catch (Exception e) {
            final InflateException ie = new InflateException(
                    getParserStateDescription(inflaterContext, attrs)
                    + ": " + e.getMessage(), e);
            ie.setStackTrace(EMPTY_STACK_TRACE);
            throw ie;
        } finally {
            // Don't retain static reference on context.
            mConstructorArgs[0] = lastContext;
            mConstructorArgs[1] = null;

            Trace.traceEnd(Trace.TRACE_TAG_VIEW);
        }

        return result;
    }
}

ViewGroup.java
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
    //---------------------------------------1
    requestLayout(); 
    invalidate(true);
    addViewInner(child, index, params, false);//-----------------------------------2
}

private void addViewInner(View child, int index, LayoutParams params,
        boolean preventRequestLayout) {

    if (mTransition != null) {
        // Don't prevent other add transitions from completing, but cancel remove
        // transitions to let them complete the process before we add to the container
        mTransition.cancel(LayoutTransition.DISAPPEARING);
    }

    if (child.getParent() != null) {
        throw new IllegalStateException("The specified child already has a parent. " +
                "You must call removeView() on the child's parent first.");
    }

    if (mTransition != null) {
        mTransition.addChild(this, child);
    }

    if (!checkLayoutParams(params)) {
        params = generateLayoutParams(params);
    }

    if (preventRequestLayout) {
        child.mLayoutParams = params;
    } else {
        child.setLayoutParams(params);
    }

    if (index < 0) {
        index = mChildrenCount;
    }

    addInArray(child, index);

    // tell our children
    if (preventRequestLayout) {
        child.assignParent(this);
    } else {
        child.mParent = this;
    }
    if (child.hasUnhandledKeyListener()) {
        incrementChildUnhandledKeyListeners();
    }

    final boolean childHasFocus = child.hasFocus();
    if (childHasFocus) {
        requestChildFocus(child, child.findFocus());
    }

    AttachInfo ai = mAttachInfo;
    if (ai != null && (mGroupFlags & FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW) == 0) {
        boolean lastKeepOn = ai.mKeepScreenOn;
        ai.mKeepScreenOn = false;
        child.dispatchAttachedToWindow(mAttachInfo, (mViewFlags&VISIBILITY_MASK));
        if (ai.mKeepScreenOn) {
            needGlobalAttributesUpdate(true);
        }
        ai.mKeepScreenOn = lastKeepOn;
    }

    if (child.isLayoutDirectionInherited()) {
        child.resetRtlProperties();
    }

    dispatchViewAdded(child);

    if ((child.mViewFlags & DUPLICATE_PARENT_STATE) == DUPLICATE_PARENT_STATE) {
        mGroupFlags |= FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE;
    }

    if (child.hasTransientState()) {
        childHasTransientStateChanged(child, true);
    }

    if (child.getVisibility() != View.GONE) {
        notifySubtreeAccessibilityStateChangedIfNeeded();
    }

    if (mTransientIndices != null) {
        final int transientCount = mTransientIndices.size();
        for (int i = 0; i < transientCount; ++i) {
            final int oldIndex = mTransientIndices.get(i);
            if (index <= oldIndex) {
                mTransientIndices.set(i, oldIndex + 1);
            }
        }
    }

    if (mCurrentDragStartEvent != null && child.getVisibility() == VISIBLE) {
        notifyChildOfDragStart(child);
    }

    if (child.hasDefaultFocus()) {
        // When adding a child that contains default focus, either during inflation or while
        // manually assembling the hierarchy, update the ancestor default-focus chain.
        setDefaultFocus(child);
    }

    touchAccessibilityNodeProviderIfNeeded(child);
}

private void addInArray(View child, int index) {
    View[] children = mChildren;
    final int count = mChildrenCount;
    final int size = children.length;
    if (index == count) {
        if (size == count) {
            mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
            System.arraycopy(children, 0, mChildren, 0, size);
            children = mChildren;
        }
        children[mChildrenCount++] = child;
    } else if (index < count) {
        if (size == count) {
            mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
            System.arraycopy(children, 0, mChildren, 0, index);
            System.arraycopy(children, index, mChildren, index + 1, count - index);
            children = mChildren;
        } else {
            System.arraycopy(children, index, children, index + 1, count - index);
        }
        children[index] = child;
        mChildrenCount++;
        if (mLastTouchDownIndex >= index) {
            mLastTouchDownIndex++;
        }
    } else {
        throw new IndexOutOfBoundsException("index=" + index + " count=" + count);
    }
}

void makeVisible() {
  //1. 将`DecorView`添加到`Window`中(通过WindowManager)
    if (!mWindowAdded) {
        ViewManager wm = getWindowManager();
        wm.addView(mDecor, getWindow().getAttributes());
        mWindowAdded = true;
    }
  //2. 将DecorView显示出来
    mDecor.setVisibility(View.VISIBLE);
}

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

WindowManagerGlobal.java
public void addView(View view, ViewGroup.LayoutParams params,
        Display display, Window parentWindow, int userId) {
    if (view == null) {
        throw new IllegalArgumentException("view must not be null");
    }
    if (display == null) {
        throw new IllegalArgumentException("display must not be null");
    }
    if (!(params instanceof WindowManager.LayoutParams)) {
        throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
    }
    ..........................
    root = new ViewRootImpl(view.getContext(), display);
    ....................
    ....................
    // do this last because it fires off messages to start doing things
    try {
         root.setView(view, wparams, panelParentView, userId);
    } catch (RuntimeException e) {
       // BadTokenException or InvalidDisplayException, clean up. 
    }
}

ViewRootImpl.java
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,
        int userId) {
            mAdded = true;
            int res; /* = WindowManagerImpl.ADD_OKAY; */

            // 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();
            
            ..............
            InputChannel inputChannel = null;
            if ((mWindowAttributes.inputFeatures
                    & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                inputChannel = new InputChannel();
            }
   
}

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

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

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

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

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

        performTraversals();

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