简单整理下activity 显示流程, 主要为acitvity -> WindowManager -> WMS -> SurfaceFlinger建立连接的过程。
本篇为鸡生蛋系列第四篇文章
第4篇都已经拖了快两年了, 几次都想写来着, 可是动力不足, 可是又想完成, 哎...
[代码: Android 11]
http://aosp.opersys.com/xref/...
setContentView()
搞应用的人都熟悉,onCreate()里, 通过setContentView()把应用布局设置下,之后就显示出来了界面,
那这个流程是咋个样子的呢?
AppCompat的setContentView()就不看了,
通过在frameworks/base/目录搜索 setContentView , 其入口主要有Dialog和Activity的,
frameworks/base/core/java/android/app/
Dialog.java
Activity.java
继续看Activity的, 其进一歩调用了window的setContentView(),
frameworks/base/core/java/android/app/Activity.java
public void setContentView(@LayoutRes int layoutResID) {
// 调用mWindow的setContentView()
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
public Window getWindow() {
return mWindow;
}
那这个mWindow是啥呢?
@UnsupportedAppUsage
final void attach(Context context, ActivityThread aThread,
......
Window window, ActivityConfigCallback activityConfigCallback, IBinder assistToken) {
......
// mWinow为PhoneWindow
mWindow = new PhoneWindow(this, window, activityConfigCallback);
它其实是 new PhoneWindow(),
这里顺便回顾下, attach()是在activity启动时会调用, (详细的可看下该系列第二篇文章 AMS startActivity())
其代码如下:
frameworks/base/core/java/android/app/ActivityThread.java
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
......
// 调用activity attach()
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback,
r.assistToken);
我们回到PhoneWindow 继续看 setContentView(),
PhoneWindow有三个setContentView()方法, 最终都是将Decor Layout和ViewGroup关系建立起来,
frameworks/base/core/java/com/android/internal/policy/PhoneWindow.java
@Override
public void setContentView(int layoutResID) {
......
if (mContentParent == null) {
// 安装Decor,
// mContentParent会在该函数里赋值 mContentParent = generateLayout(mDecor);
installDecor();
}
......
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
// 将我们应用程序的布局加入
mLayoutInflater.inflate(layoutResID, mContentParent);
}
......
}
// 应用程序除了通过指定资源ID方式调用setContentView()
// 也可通过传入参数View方式调用,
// 最终也是将该view加入 mContentParent
@Override
public void setContentView(View view) {
setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
}
@Override
public void setContentView(View view, ViewGroup.LayoutParams params) {
......
if (mContentParent == null) {
// 和参数为资源ID方式一样,先安装Decor
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 {
// 加入view
mContentParent.addView(view, params);
}
mContentParent.requestApplyInsets();
......
}
关于 setContentView()更详细的代码解读可看
https://www.jianshu.com/p/2ee...
我觉得这篇文章写得很好, 这里就不再讲了.
show
本来以为应用 onCreate() --> setContentView()之后, 应用就显示出来了, 可是来来回回研究代码好像都不太对,
这时候再来看看文章前面提到的Dialog咋显示的呢?
我们知道对于Dialog用法一般为:
// 伪代码描述
Dialog mDialog = new Dialog();
mDialog 资源参数等设置
// 调用show就显示出来了
mDialog.show();
先new 一个Dialog()对象,然后设置资源参数等, 再调用其show()方法就可以将其显示出来.
那我们就先看看其show()方法是咋玩的.
frameworks/base/core/java/android/app/Dialog.java
public void show() {
......// 获取mDecor
mDecor = mWindow.getDecorView();
......// 属性
WindowManager.LayoutParams l = mWindow.getAttributes();
......
// 添加view
mWindowManager.addView(mDecor, l);
show() 里通过WindowManager的addView()方法, 与WinowManager联系上.
上面的mWindowManager即为WINDOW_SERVICE,
mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
需要注意的是 mWindowManager 为 WindowManagerImpl, 此时还处于用户进程中, 非WindowManagerService.
可通过看其 registerService() 注册服务时, 其确实为 new WindowManagerImpl()
frameworks/base/core/java/android/app/SystemServiceRegistry.java
registerService(Context.WINDOW_SERVICE, WindowManager.class,
new CachedServiceFetcher<WindowManager>() {
@Override
public WindowManager createService(ContextImpl ctx) {
return new WindowManagerImpl(ctx);
}});
那么activity的mWindowManager.addView()在哪儿呢
这个时候就要推荐一本书了
<<深入理解Android内核设计思想>> 林学森 著
这里面surface window view当然还有别的方面内容都讲得不错,
要是我能达到作者的高度这辈子也就值了,哎......
引用书中的话
那么Activity 应用进程在什么时候会调用 addView,进而由WMS来处理addWindow 呢?
Activity从启动到最终在屏幕上显示出来,分别要经历onCreate->onStart->onResume三个状态迁移。其中 onResume是当界面即将可见时才会调用的,紧接着 ActivityThread 就会通过WindowManagerImpl来把应用程序窗口添加到系统中。
具体代码如下:
frameworks/base/core/java/android/app/ActivityThread.java
public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward,
String reason) {
......
// performResumeActivity()最终会调用activity的onResume()
final ActivityClientRecord r = performResumeActivity(token, finalStateRequest, reason);
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
// 获取decor, DecorView是activity 整棵View树最外围
View decor = r.window.getDecorView();
// 可见性
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
......
if (a.mVisibleFromClient) {
if (!a.mWindowAdded) {
a.mWindowAdded = true;
// *** 添加到view里
wm.addView(decor, l);
从上面代码分析可知,其最终也是通过wm.addView(), 最终和WMS联系上, 和前面的Dialog流程大体差不多,
稍微有点小区别是其通过 createLocalWindowManager()创建出来的.
frameworks/base/core/java/android/view/Window.java
public void setWindowManager(WindowManager wm, IBinder appToken, String appName,
boolean hardwareAccelerated) {
......
if (wm == null) {
wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);
}
// wm最终为createLocalWindowManager()创建出来的
mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);
从上面代码可知Dialog的show()和Activity 显示都最终调用了 WindowManagerImpl 的 addView()方法,
那这之后是咋和SurfaceFlinger联系在一起的呢? 我们接着addView()看看。
addView() -> WMS
这些代码真是一层套一层, WindowManagerImpl addView() 最终又调用了 WindowManagerGlobal addView()
frameworks/base/core/java/android/view/WindowManagerImpl.java
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplayNoVerify(), mParentWindow,
mContext.getUserId());
}
frameworks/base/core/java/android/view/WindowManagerGlobal.java
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow, int userId) {
......
root = new ViewRootImpl(view.getContext(), display);
// do this last because it fires off messages to start doing things
try {
// ViewRootImpl setView()
root.setView(view, wparams, panelParentView, userId);
WindowManagerGlobal setView() 进一通过 ViewRootImpl setView()
frameworks/base/core/java/android/view/ViewRootImpl.java
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,
int userId) {
synchronized (this) {
if (mView == null) {
mView = view;
......// final IWindowSession mWindowSession;
res = mWindowSession.addToDisplayAsUser(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(), userId, mTmpFrame,
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mDisplayCutout, inputChannel,
mTempInsets, mTempControls);
进一步调用IWindowSession addToDisplayAsUser(), 其最终实现为
frameworks/base/services/core/java/com/android/server/wm/Session.java
public int addToDisplayAsUser(IWindow window,......) {
return mService.addWindow(...);
}
上面的mService为
final WindowManagerService mService;
到这里才终于和WMS扯上点关系,
从上分析, ViewRootImpl通过IWindowSession为桥梁,建立与WMS联系
ViewRootImpl <-> IWindowSession <-> WindowManagerService
WMS -> SurfaceFlinger
从上面终于看到应用activity通过一系列的调用, 终于和WMS关联上了, 那与SurfaceFlinger咋关联上的呢?
那就继续看addWindow()流程吧
frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public int addWindow(Session session, IWindow client, int seq,
LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame,
Rect outContentInsets, Rect outStableInsets,
DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel,
InsetsState outInsetsState, InsetsSourceControl[] outActiveControls,
int requestUserId) {
// 好多好多的检查
....
// WMS用WindowState管理window
final WindowState win = new WindowState(this, session, client, token, parentWindow,
appOp[0], seq, attrs, viewVisibility, session.mUid, userId,
session.mCanAddInternalSystemWindow);
....
if (openInputChannels) {
// 与 input建立联系
win.openInputChannel(outInputChannel);
}
....
// 与SurfaceFlinger建立联系
win.attach();
addWindow()是一个比较长也比较重要的函数, 从中我们可以了解到 WMS用 WindowState 描述窗口, 并通过openInputChannel()与输入关联上,
而其与SurfaceFlinger是通过 WindowState.attach() --> Session.windowAddedLocked() --> SurfaceSession() --> SurfaceComposerClient()
联系上的.
代码如下:
frameworks/base/services/core/java/com/android/server/wm/WindowState.java
void attach() {
if (DEBUG) Slog.v(TAG, "Attaching " + this + " token=" + mToken);
mSession.windowAddedLocked(mAttrs.packageName);
}
frameworks/base/services/core/java/com/android/server/wm/Session.java
void windowAddedLocked(String packageName) {......
if (mSurfaceSession == null) {......
mSurfaceSession = new SurfaceSession();
SurfaceSession()就会与SF建立联系, 可看下代码注释, 不再详细解说.
frameworks/base/core/java/android/view/SurfaceSession.java
public SurfaceSession() {
// 进构造函数调用JNI nativeCreate()
mNativeClient = nativeCreate();
}
frameworks/base/core/jni/android_view_SurfaceSession.cpp
static jlong nativeCreate(JNIEnv* env, jclass clazz) {
// JNI里new了个SurfaceComposerClient, 我们知道其为SurfaceFlinger的client端,
// 用于和SF通信.
// 如果不熟悉该部分的可继续往后看代码
SurfaceComposerClient* client = new SurfaceComposerClient();
frameworks/native/libs/gui/SurfaceComposerClient.cpp
// SurfaceComposerClient的构造函数里并没有做啥, 其继承RefBase, 所以接下来看其onFirstRef()
void SurfaceComposerClient::onFirstRef() {
// 这里的ComposerService::getComposerService()得到的为 mComposerService, 也即是SurfaceFlinger服务
sp<ISurfaceComposer> sf(ComposerService::getComposerService());
if (sf != nullptr && mStatus == NO_INIT) {
sp<ISurfaceComposerClient> conn;
// 创建连接
conn = sf->createConnection();
/*static*/ sp<ISurfaceComposer> ComposerService::getComposerService() {
// getInstance()获取实例
ComposerService& instance = ComposerService::getInstance();
......
// 返回实例的 mComposerService
return instance.mComposerService;
// 因为ComposerService继承自单例, 调用其getInstance()如果没创建对象的话, 会创建一个,
// 所以看下其构造函数
ComposerService::ComposerService()
: Singleton<ComposerService>() {
Mutex::Autolock _l(mLock);
// 构造函数里调用connectLocked()
connectLocked();
}
void ComposerService::connectLocked() {
// 获取SurfaceFlinger服务并赋值给 mComposerService
const String16 name("SurfaceFlinger");
while (getService(name, &mComposerService) != NO_ERROR) {
再回头看下
void SurfaceComposerClient::onFirstRef() {
conn = sf->createConnection();
其在SurfaceFlinger创建了一个client进行管理
frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp
sp<ISurfaceComposerClient> SurfaceFlinger::createConnection() {
const sp<Client> client = new Client(this);
return client->initCheck() == NO_ERROR ? client : nullptr;
}
NOTE
Window <1--1> WMS的WindowState <1--1> SurfaceSession <1--1> SurfaceComposerClient <1--1> SurfaceFlinger进程里的Client
它们是一一对应的
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