深入理解WMS（四）：从WMS的角度分析Activity之间的关系

sWindowManagerService = getWindowManagerService();

ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale());

} catch (RemoteException e) {

throw e.rethrowFromSystemServer();

}

}

return sWindowManagerService;

}

}

}

Activity a = performLaunchActivity(r, customIntent);使用ClassLoader加载XXXActivity，这其中会创建ContextImpl、如果Application还没启动过，会先把Applicaition创建并onCreate,然后调用XXXActivity的attach();

在attach中：会创建改activity的对应的window即PhoneWindow，以及phoneWindow和WindowManagerImpl关联：

Activity:

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);

mMainThread = aThread;

mInstrumentation = instr;

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();

mCurrentConfig = config;

}

其中：(WindowManager)context.getSystemService(Context.WINDOW_SERVICE)获取到是WindowManagerImpl：

这边会走到ContextImpl.getSystemService：

class ContextImpl extends Context {

@Override

public Object getSystemService(String name) {

return SystemServiceRegistry.getSystemService(this, name);

}

}

SystemServiceRegistry:

final class SystemServiceRegistry {

public static Object getSystemService(ContextImpl ctx, String name) {

ServiceFetcher<?> fetcher = SYSTEM_SERVICE_FETCHERS.get(name);

return fetcher != null ? fetcher.getService(ctx) : null;

}

private static final HashMap<Class<?>, String> SYSTEM_SERVICE_NAMES =

new HashMap<Class<?>, String>();

private static final HashMap<String, ServiceFetcher<?>> SYSTEM_SERVICE_FETCHERS =

new HashMap<String, ServiceFetcher<?>>();

private static int sServiceCacheSize;

static {

registerService(Context.ACCESSIBILITY_SERVICE, AccessibilityManager.class,

new CachedServiceFetcher() {

@Override

public AccessibilityManager createService(ContextImpl ctx) {

return AccessibilityManager.getInstance(ctx);

}});

registerService(Context.WINDOW_SERVICE, WindowManager.class,

new CachedServiceFetcher() {

@Override

public WindowManager createService(ContextImpl ctx) {

return new WindowManagerImpl(ctx);

}});

}

返回是new WindowManagerImpl(ctx);在performLaunchActivity函数中，走完attach后，继续调用mInstrumentation.callActivityOnCreate去实行XXXActivity的onCreate，这时候大家会写setContentView(R.layout.xxx)

Step3:

Activity.setContentView():

会调用getWindow().setContentView(layoutResID),即PhoneWindow类中的setContentView：主要是在PhoneWindow创建DecorView mDecor(This is the top-level view of the window, containing the window decor),然后从mDecor找出android.R.id.content: mContentParent(ViewGroup), 然后把activity设置的View添加到mContentParent.addView(view, params);

public void setContentView(@LayoutRes int layoutResID) {

getWindow().setContentView(layoutResID);

initWindowDecorActionBar();

}

PhoneWindow:

public class PhoneWindow extends Window implements MenuBuilder.Callback {

public void setContentView(int layoutResID) {

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;

}

}

Step4：

在ActivitThread.handleLaunchActivity函数走完performLaunchActivity后，接着走handleResumeActivity函数中，显示启动r = performResumeActivity(token, clearHide, reason);去走XXXActivity的onResume。

接着会对Activity的对应的window设置窗口类型：**l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION，**WMS是对窗口进行操作，每个activity对应一个窗口，Framework会定义好几种窗口类型，比如系统Window、应用程序window、子Window等。这边的type类型很重要，没有这个，window显示不出来的。

接着会调用到ViewManager wm = a.getWindowManager();wm.addView(decor, l);走到WindowManagerImpl.addView：

ActivityThread:

final void handleResumeActivity(IBinder token,

boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) {

ActivityClientRecord r = mActivities.get(token);

…

r = performResumeActivity(token, clearHide, reason);

…

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;

ViewRootImpl impl = decor.getViewRootImpl();

if (impl != null) {

impl.notifyChildRebuilt();

}

}

if (a.mVisibleFromClient && !a.mWindowAdded) {

a.mWindowAdded = true;

wm.addView(decor, l);

}

…

}

Step5：

WindowManagerImpl的addView又调用到WindowManagerGlobal.getInstance()的addView：

这个函数会创建root = new ViewRootImpl(view.getContext(), display);然后保存到mRoots.add(root)

接着调用到 root.setView(view, wparams, panelParentView);

public final class WindowManagerImpl implements WindowManager {

private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();

@Override

public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {

applyDefaultToken(params);

mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);

}

}

public final class WindowManagerGlobal {

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);

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) {

}

}

}

Step6：

ViewRootImpl.setView():

这个函数中，通过WindowManagerGloabl拿到IWindowSession mWindowSession及远程WMS的Seesion的对象，进行mWindowSession.addToDisplay，到system_server进程的Session中。

public final class ViewRootImpl implements ViewParent,

View.AttachInfo.Callbacks, ThreadedRenderer.HardwareDrawCallbacks {

public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {

synchronized (this) {

…

try {

res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,

getHostVisibility(), mDisplay.getDisplayId(),

mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,

mAttachInfo.mOutsets, mInputChannel);

}

}

…

}

}

最后

下面是有几位Android行业大佬对应上方技术点整理的一些进阶资料。希望能够帮助到大家提升技术

高级UI，自定义View

UI这块知识是现今使用者最多的。当年火爆一时的Android入门培训，学会这小块知识就能随便找到不错的工作了。

不过很显然现在远远不够了，拒绝无休止的CV,亲自去项目实战，读源码，研究原理吧！

《Android学习笔记总结+移动架构视频+大厂面试真题+项目实战源码》，点击传送门，即可获取！
achInfo.mStableInsets,

mAttachInfo.mOutsets, mInputChannel);

}

}

…

}

}

最后

下面是有几位Android行业大佬对应上方技术点整理的一些进阶资料。希望能够帮助到大家提升技术

[外链图片转存中…(img-zeNGtZw8-1715337669853)]

高级UI，自定义View

UI这块知识是现今使用者最多的。当年火爆一时的Android入门培训，学会这小块知识就能随便找到不错的工作了。

不过很显然现在远远不够了，拒绝无休止的CV,亲自去项目实战，读源码，研究原理吧！

[外链图片转存中…(img-XBEI75pf-1715337669853)]

《Android学习笔记总结+移动架构视频+大厂面试真题+项目实战源码》，点击传送门，即可获取！