Activity頁面載入流程(二)

摘要： 接上一篇《Activity頁面載入流程(一)》 上一篇講了Window的建立，但其顯示流程還沒有講清楚就跑路了 廢話不多說，我們continue PS：:blush::blush:英文用錯了場景別笑話...

接上一篇《Activity頁面載入流程(一)》

上一篇講了Window的建立，但其顯示流程還沒有講清楚就跑路了

廢話不多說，我們continue

PS：:blush::blush:英文用錯了場景別笑話，誰讓它是關鍵詞字:blush::blush:

WindowManager、WindowManagerImpl和WindowManagerGlobal的關係及內部機制

WindowManager是一個繼承於ViewManager的介面，實現類是WindowManagerImpl

Activity.java

final void attach(...){
...
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),//系統的WindowManger
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
...
mWindowManager = mWindow.getWindowManager();
}

Window.java

public void setWindowManager(WindowManager wm, IBinder appToken, String appName, boolean hardwareAccelerated) {
...
//wm的createLocalWindowManager方法又重新new了WindowManagerImpl
mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);
}

public WindowManager getWindowManager() {
return mWindowManager;
}

WindowManagerImpl.java

WindowManagerImpl是WindowManager的實現類，顯實現了addView、updateViewLayout、removeView等方法，可是這哥們胸懷宇宙，有空還要看星星，別看它是一個實現類，名字還帶一個Impl，卻把具體工作都交給了單例的WindowManagerGlobal。

public final class WindowManagerImpl implements WindowManager {
//全域性單例
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);
}

@Override
public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.updateViewLayout(view, params);
}

@Override
public void removeView(View view) {
mGlobal.removeView(view, false);
}
...
}

WindowManagerGlobal.java

WindowManagerGlobal是單例的，所以它內部用幾個集合來儲存Window及引數和所對應的View

//每個Window對應的View
private final ArrayList<View> mViews = new ArrayList<View>();
//每個Window對應的ViewRootImpl
private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();
//每個Window的引數
private final ArrayList<WindowManager.LayoutParams> mParams = new ArrayList<WindowManager.LayoutParams>();

public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {

ViewRootImpl root;
...
//建立ViewRootImpl，View的invalidate更新view的時候，就是從ViewRootImpl開始的
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
....
//上面的三個集合
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);

// do this last because it fires off messages to start doing things
try {
//重要方法，
root.setView(view, wparams, panelParentView);
}
...
}

Window的顯示

WindowManagerService作為一個系統級的服務執行在一個單獨的程序，所以WindowManager和它之間的互動是一個IPC(程序間通訊)過程，ViewRootImpl充當了橋樑的作為

通過Binder機制獲取WMS，在WindowManagerService獲取舒適化Session,進而通過session的addToDisplay方法和WMS的addWindow新增到將Window新增到裝置

ViewRootImpl.java

final IWindowSession mWindowSession;

public ViewRootImpl(Context context, Display display) {
...
//在構造方法裡呼叫WindowManagerGlobal的static方法getWindowSession()初始化IWindowSession
mWindowSession = WindowManagerGlobal.getWindowSession();
...
}

public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
...
//開始View的三大流程，測量、佈局和繪製
requestLayout();
...
try {
...
//顯示
res = mWindowSession.addToDisplay(mWindow,...);
...
} 
...
}

WindowManagerGlobal.java

public static IWindowSession getWindowSession() {
synchronized (WindowManagerGlobal.class) {
if (sWindowSession == null) {
try {
InputMethodManager imm = InputMethodManager.getInstance();
IWindowManager windowManager = getWindowManagerService();
//從WindowManagerService裡獲取WindowSession
sWindowSession = windowManager.openSession(
new IWindowSessionCallback.Stub() {
@Override
public void onAnimatorScaleChanged(float scale) {
ValueAnimator.setDurationScale(scale);
}
},
imm.getClient(), imm.getInputContext());ffgetWindowManagerService
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
return sWindowSession;
}
}

public static IWindowManager getWindowManagerService() {
synchronized (WindowManagerGlobal.class) {
if (sWindowManagerService == null) {
//從binder裡獲取WindowManagerService
sWindowManagerService = IWindowManager.Stub.asInterface(ServiceManager.getService("window"));
try {
if (sWindowManagerService != null) {
ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale());
}
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
return sWindowManagerService;
}
}

WindowManagerService.java

@Override
public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client, IInputContext inputContext) {
if (client == null) throw new IllegalArgumentException("null client");
if (inputContext == null) throw new IllegalArgumentException("null inputContext");
//Session就在這裡建立，Session和WindowManagerService相互持有
Session session = new Session(this, callback, client, inputContext);
return session;
}

Session.java

@Override
public int addToDisplay(IWindow window, ...) {
//這裡呼叫WMS的addWindow方法
return mService.addWindow(this, window, ...);
}

Window已經顯示了

Activity的頁面載入流程已經結束，涉及到的類比較多，可能有說的不明的或錯誤的地方，請諒解

原始碼一個class動輒萬行，內部類N多個

是不是腦殼疼

疼就對了

不然你以為你zou是谷歌開發工程師了

然

不進則退

學習還是必須的

沒有什麼比自身的強大更重要

你想要的

時間都會給你

學會自我約束

才能自我自由

雞湯是給你們喝的，我喜歡吃肉

End