To understand this chapter, you need to first understand the LayoutInflater tool class, which I have previously analyzed: http://www.cnblogs.com/kezhuang/p/69783.html
Window s is a global variable in the Activity class. Its function is to assist Activity (or possibly other components. Take Activity as an example) to assemble the interface. This is the general process.
1.Activity tells Window s the request to draw the interface
2. Windows creates the structure tree of View and notifies View to redraw to display on Activity.
We use Activity's setContentView to analyze Window s
//call Window Below setContentView The way to do it, let's look at it. getWindow()Method public void setContentView(View view) { getWindow().setContentView(view); initWindowDecorActionBar(); }
The method in Activity is implemented by calling setContentView of getWindow
//It's a simple return, so this mWindow Where is the value assigned? public Window getWindow() { return mWindow; }
The implementation class of mWindow s is PhoneWindow, and only this implementation class is the object created in a hidden method of Activity.
//this attach The method is activity The internal definition is Activity It's called when it's created, as we can see Window The implementation class is PhoneWindow， //We can go there. PhoneWindow Let's take a look at it. setContentView Specific realization 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); mWindow.setCallback(this); mWindow.setOnWindowDismissedCallback(this); mWindow.getLayoutInflater().setPrivateFactory(this); //... mWindow.setWindowManager( (WindowManager)context.getSystemService(Context.WINDOW_SERVICE), mToken, mComponent.flattenToString(), (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0); if (mParent != null) { mWindow.setContainer(mParent.getWindow()); } mWindowManager = mWindow.getWindowManager(); }
This attach is actually called in ActivityThread, and I won't go into details. This is part of the Activity startup process. Interested people can flip it over by themselves.
As you can see from the above, mWindow s is PhoneWindow, so setContentView is the method of calling PhoneWindow.
Actually, it is not suitable to call this class Phone Windows. Because our Android system has been implanted into a variety of devices. Already out of mobile phones, should be renamed DeviceWindow, haha
Let's go on and look down.
//hold resId Loading into view Tree, and then redraw the display interface @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. // When loading, the variable is empty and needs to be called installDecor To assign values 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 { //already mContentParent Father View，hold Activity The layout passed in is resolved to mContentParent in mLayoutInflater.inflate(layoutResID, mContentParent); } //to view Make a request, ask for redrawing mContentParent.requestApplyInsets(); final Callback cb = getCallback(); //Finally, call the callback method to indicate that the interface has changed. if (cb != null && !isDestroyed()) { cb.onContentChanged(); } }
This section first determines whether mContentParent is empty. This variable is a ViewGroup type, located in DecorView, and its main function is to store the user's layout (resId passed by setContentView in Activity).
First, a DecorView is created by installDecor. Then create the mContentParent object and load the layoutResID passed by Activity into the mContentParent container.
At this point, a complete DecorView tree is assembled. Wait until ViewRootImpl is notified to initiate redrawing, and then send a message to Windows Manager Service to display the interface
Let's look at the installDecor method. It's a long one. I'll omit some judgments and just keep the core. Let's get to know a few functions that we'll use in a few moments in advance.
//The first is to create Decor The function of the object is very simple. new Once protected DecorView generateDecor() { return new DecorView(getContext(), -1); } //The second is to create mContentParent Object functions, which are somewhat complex, also need to determine the system version to choose different styles and layouts protected ViewGroup generateLayout(DecorView decor) { // Apply data from current theme. //A lot of judgments have been omitted from the front, which are all judgments of interface style. 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 ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) { if (mIsFloating) { TypedValue res = new TypedValue(); getContext().getTheme().resolveAttribute( R.attr.dialogTitleIconsDecorLayout, res, true); layoutResource = res.resourceId; } else { layoutResource = R.layout.screen_title_icons; } // XXX Remove this once action bar supports these features. removeFeature(FEATURE_ACTION_BAR); // System.out.println("Title Icons!"); } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0 && (features & (1 << FEATURE_ACTION_BAR)) == 0) { // Special case for a window with only a progress bar (and title). // XXX Need to have a no-title version of embedded windows. layoutResource = R.layout.screen_progress; // System.out.println("Progress!"); } else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) { // Special case for a window with a custom title. // If the window is floating, we need a dialog layout if (mIsFloating) { TypedValue res = new TypedValue(); getContext().getTheme().resolveAttribute( R.attr.dialogCustomTitleDecorLayout, res, true); layoutResource = res.resourceId; } else { layoutResource = R.layout.screen_custom_title; } // XXX Remove this once action bar supports these features. removeFeature(FEATURE_ACTION_BAR); } else if ((features & (1 << FEATURE_NO_TITLE)) == 0) { // If no other features and not embedded, only need a title. // If the window is floating, we need a dialog layout if (mIsFloating) { TypedValue res = new TypedValue(); getContext().getTheme().resolveAttribute( R.attr.dialogTitleDecorLayout, res, true); layoutResource = res.resourceId; } else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) { layoutResource = a.getResourceId( R.styleable.Window_windowActionBarFullscreenDecorLayout, R.layout.screen_action_bar); } else { layoutResource = R.layout.screen_title; } // System.out.println("Title!"); } else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) { layoutResource = R.layout.screen_simple_overlay_action_mode; } else { // Embedded, so no decoration is needed. layoutResource = R.layout.screen_simple; // System.out.println("Simple!"); } //The above will select a suitable one. layout To load from the following code mDecor.startChanging(); //Loading into view tree After that, add the results to the decor In the middle, and then put in Assignment to mContentRoot Variable Storage View in = mLayoutInflater.inflate(layoutResource, null); decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); mContentRoot = (ViewGroup) in; //this findView From mDecor In search, find the middle area, is used for storage. Activity Place of Layout //That's our mContentParent variable ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT); //This will not be redrawn systematically mDecor.finishChanging(); return contentParent; }
These two methods need to be understood in advance. One is the process of creating DecorView and the other is the process of creating mContentParent. The annotations above are very detailed. Just look at the annotations.
//This method is known from the name of the method. Install one called Decor Things //mDecor It's our entire application interface.,mContentParent Namely Activity Location of interface display private void installDecor() { //The final display interface of mobile phone, including status bar, etc. if (mDecor == null) { //new One DecorView Objects come out mDecor = generateDecor(); mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) { mDecor.postOnAnimation(mInvalidatePanelMenuRunnable); } } //tode ti mContentParent It's carrying us. Activity A container for layout if (mContentParent == null) { //Here the bearer is created Activity Layout of containers, specific analysis see the analysis above mContentParent = generateLayout(mDecor); // Set up decor part of UI to ignore fitsSystemWindows if appropriate. mDecor.makeOptionalFitsSystemWindows(); final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById( R.id.decor_content_parent); if(decorContentParent!=null){ Log.i(TAG,"decorContentParent:"+decorContentParent.toString()); }else{ Log.i(TAG,"decorContentParent is null"); } if (decorContentParent != null) { mDecorContentParent = decorContentParent; mDecorContentParent.setWindowCallback(getCallback()); if (mDecorContentParent.getTitle() == null) { mDecorContentParent.setWindowTitle(mTitle); } final int localFeatures = getLocalFeatures(); for (int i = 0; i < FEATURE_MAX; i++) { if ((localFeatures & (1 << i)) != 0) { mDecorContentParent.initFeature(i); } } mDecorContentParent.setUiOptions(mUiOptions); if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) != 0 || (mIconRes != 0 && !mDecorContentParent.hasIcon())) { mDecorContentParent.setIcon(mIconRes); } else if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) == 0 && mIconRes == 0 && !mDecorContentParent.hasIcon()) { mDecorContentParent.setIcon( getContext().getPackageManager().getDefaultActivityIcon()); mResourcesSetFlags |= FLAG_RESOURCE_SET_ICON_FALLBACK; } if ((mResourcesSetFlags & FLAG_RESOURCE_SET_LOGO) != 0 || (mLogoRes != 0 && !mDecorContentParent.hasLogo())) { mDecorContentParent.setLogo(mLogoRes); } // Invalidate if the panel menu hasn't been created before this. // Panel menu invalidation is deferred avoiding application onCreateOptionsMenu // being called in the middle of onCreate or similar. // A pending invalidation will typically be resolved before the posted message // would run normally in order to satisfy instance state restoration. PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false); if (!isDestroyed() && (st == null || st.menu == null) && !mIsStartingWindow) { invalidatePanelMenu(FEATURE_ACTION_BAR); } } else { mTitleView = (TextView)findViewById(R.id.title); if (mTitleView != null) { mTitleView.setLayoutDirection(mDecor.getLayoutDirection()); if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) { View titleContainer = findViewById( R.id.title_container); if (titleContainer != null) { titleContainer.setVisibility(View.GONE); } else { mTitleView.setVisibility(View.GONE); } if (mContentParent instanceof FrameLayout) { ((FrameLayout)mContentParent).setForeground(null); } } else { mTitleView.setText(mTitle); } } } if (mDecor.getBackground() == null && mBackgroundFallbackResource != 0) { mDecor.setBackgroundFallback(mBackgroundFallbackResource); } // Only inflate or create a new TransitionManager if the caller hasn't // already set a custom one. if (hasFeature(FEATURE_ACTIVITY_TRANSITIONS)) { if (mTransitionManager == null) { final int transitionRes = getWindowStyle().getResourceId( R.styleable.Window_windowContentTransitionManager, 0); if (transitionRes != 0) { final TransitionInflater inflater = TransitionInflater.from(getContext()); mTransitionManager = inflater.inflateTransitionManager(transitionRes, mContentParent); } else { mTransitionManager = new TransitionManager(); } } mEnterTransition = getTransition(mEnterTransition, null, R.styleable.Window_windowEnterTransition); mReturnTransition = getTransition(mReturnTransition, USE_DEFAULT_TRANSITION, R.styleable.Window_windowReturnTransition); mExitTransition = getTransition(mExitTransition, null, R.styleable.Window_windowExitTransition); mReenterTransition = getTransition(mReenterTransition, USE_DEFAULT_TRANSITION, R.styleable.Window_windowReenterTransition); mSharedElementEnterTransition = getTransition(mSharedElementEnterTransition, null, R.styleable.Window_windowSharedElementEnterTransition); mSharedElementReturnTransition = getTransition(mSharedElementReturnTransition, USE_DEFAULT_TRANSITION, R.styleable.Window_windowSharedElementReturnTransition); mSharedElementExitTransition = getTransition(mSharedElementExitTransition, null, R.styleable.Window_windowSharedElementExitTransition); mSharedElementReenterTransition = getTransition(mSharedElementReenterTransition, USE_DEFAULT_TRANSITION, R.styleable.Window_windowSharedElementReenterTransition); if (mAllowEnterTransitionOverlap == null) { mAllowEnterTransitionOverlap = getWindowStyle().getBoolean( R.styleable.Window_windowAllowEnterTransitionOverlap, true); } if (mAllowReturnTransitionOverlap == null) { mAllowReturnTransitionOverlap = getWindowStyle().getBoolean( R.styleable.Window_windowAllowReturnTransitionOverlap, true); } if (mBackgroundFadeDurationMillis < 0) { mBackgroundFadeDurationMillis = getWindowStyle().getInteger( R.styleable.Window_windowTransitionBackgroundFadeDuration, DEFAULT_BACKGROUND_FADE_DURATION_MS); } if (mSharedElementsUseOverlay == null) { mSharedElementsUseOverlay = getWindowStyle().getBoolean( R.styleable.Window_windowSharedElementsUseOverlay, true); } } } }
Above is the creation of DecorView and mContentParent objects
At this point, the setContentView method is executed and a DecorView tree is finally produced. Describe the layout hierarchy of the current interface. But it's not going to redraw the interface yet.
These are all done in the onCreate method. Is the life cycle of Activity not finished until onResume?
Our Activity's onCreate method is called in ActivityThread, so after executing the onCreate method, we will go back to the Activity Thread method, and ActivityThread will continue to call the Activity's onResume lifecycle method.
But before calling the onResume method. ActivityThread does one step in the middle, which is to draw the number of views assembled by setContent View in onCreate method, which is the mDecor object under Activity object.
final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward, boolean reallyResume) { // 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 ActivityClientRecord r = performResumeActivity(token, clearHide); 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) { } } 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 (a.mVisibleFromClient) { a.mWindowAdded = true; wm.addView(decor, l); } // If the window has already been added, but during resume // we started another activity, then don't yet make the // window visible. } else if (!willBeVisible) { if (localLOGV) Slog.v( TAG, "Launch " + r + " mStartedActivity set"); r.hideForNow = true; } // Get rid of anything left hanging around. cleanUpPendingRemoveWindows(r); // The window is now visible if it has been added, we are not // simply finishing, and we are not starting another activity. if (!r.activity.mFinished && willBeVisible && r.activity.mDecor != null && !r.hideForNow) { if (r.newConfig != null) { r.tmpConfig.setTo(r.newConfig); if (r.overrideConfig != null) { r.tmpConfig.updateFrom(r.overrideConfig); } if (DEBUG_CONFIGURATION) Slog.v(TAG, "Resuming activity " + r.activityInfo.name + " with newConfig " + r.tmpConfig); performConfigurationChanged(r.activity, r.tmpConfig); freeTextLayoutCachesIfNeeded(r.activity.mCurrentConfig.diff(r.tmpConfig)); r.newConfig = null; } if (localLOGV) Slog.v(TAG, "Resuming " + r + " with isForward=" + isForward); WindowManager.LayoutParams l = r.window.getAttributes(); if ((l.softInputMode & WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != forwardBit) { l.softInputMode = (l.softInputMode & (~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION)) | forwardBit; if (r.activity.mVisibleFromClient) { ViewManager wm = a.getWindowManager(); View decor = r.window.getDecorView(); wm.updateViewLayout(decor, l); } } r.activity.mVisibleFromServer = true; mNumVisibleActivities++; if (r.activity.mVisibleFromClient) { r.activity.makeVisible(); } } if (!r.onlyLocalRequest) { r.nextIdle = mNewActivities; mNewActivities = r; if (localLOGV) Slog.v( TAG, "Scheduling idle handler for " + r); Looper.myQueue().addIdleHandler(new Idler()); } r.onlyLocalRequest = false; // Tell the activity manager we have resumed. if (reallyResume) { try { ActivityManagerNative.getDefault().activityResumed(token); } catch (RemoteException ex) { } } } else { // If an exception was thrown when trying to resume, then // just end this activity. try { ActivityManagerNative.getDefault() .finishActivity(token, Activity.RESULT_CANCELED, null, false); } catch (RemoteException ex) { } } }
Look carefully at the code that I marked the color and bold font, get the Windows object under Activity, get the DecorView object just assembled, and then create a ViewRootImpl object through the addView method of wm, which is the Windows Manager object.
Then the ViewRootImpl object displays the interface by redrawing and notifying Windows Manager Services, and the Windows class is explained.
The purpose of the Window s class is to help ViewRootImpl assemble the View model. Then ViewRootImpl is responsible for traversing the display
If there are any mistakes or questions, please point out in the comments section that I will correct them, learn together and make progress together. Thank you for your support.