（2）Activity创建Window和View分析

一.Activity启动

Activity由ActivityThread负责启动。 ActivityThread的分析将在《ActivityThread分析》中，在此，只需要知道创建activity的入口在ActivityThread就行，不影响以下的分析。

ActivityThread.java

private final Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {

Activity activity = null;

try {

java.lang.ClassLoader cl = r.packageInfo.getClassLoader();

activity = mInstrumentation.newActivity(

cl, component.getClassName(), r.intent);

r.intent.setExtrasClassLoader(cl);

if (r.state != null) {

r.state.setClassLoader(cl);

}

} catch (Exception e) {

if (!mInstrumentation.onException(activity, e)) {

throw new RuntimeException(

"Unable to instantiate activity " + component

+ ": " + e.toString(), e);

}

}

return activity;

}

二。调用Activity的attach方法。

ActivityThread.java

private final Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {

ContextImpl appContext = new ContextImpl();

appContext.init(r.packageInfo, r.token, this);

appContext.setOuterContext(activity);

CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());

Configuration config = new Configuration(mConfiguration);

if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "

+ r.activityInfo.name + " with config " + config);

activity.attach(appContext, this, getInstrumentation(), r.token,

r.ident, app, r.intent, r.activityInfo, title, r.parent,

r.embeddedID, r.lastNonConfigurationInstance,

r.lastNonConfigurationChildInstances, config);

}

三。Activity的attach实现

1.attach的实现

Activity.java //Activity implement Window.Callback

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,

Object lastNonConfigurationInstance,

HashMap<String,Object> lastNonConfigurationChildInstances,

Configuration config) {

attachBaseContext(context); //ContextThemeWrapper中实现，赋值给mBase

mWindow = PolicyManager.makeNewWindow(this); //创建window，实际上是一个PhoneWindow对象

mWindow.setCallback(this); //设置Window.Callback，因为Activity implement Window.Callback

mWindow.setWindowManager(null, mToken, mComponent.flattenToString());

mWindowManager = mWindow.getWindowManager();

}

2.PolicyManager.makeNewWindow实现

(1).PolicyManager.java

private static final String POLICY_IMPL_CLASS_NAME =

"com.android.internal.policy.impl.Policy";

private static final IPolicy sPolicy;

static {

// Pull in the actual implementation of the policy at run-time

Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME);

sPolicy = (IPolicy)policyClass.newInstance();

}

public static Window makeNewWindow(Context context) {

return sPolicy.makeNewWindow(context);

}

(2).Policy.java //Policy implements IPolicy

public PhoneWindow makeNewWindow(Context context) {

return new PhoneWindow(context);

}

3.设置WindowManager

mWindow.setWindowManager(null, mToken, mComponent.flattenToString()); //为Window中的WindowManager赋值

mWindowManager = mWindow.getWindowManager(); //为Acitivity中的WindowManager赋值

WindowManager只是一个interface，实现类有两个：Window.LocalWindowManager和WindowManagerImpl。

(1).Window.LocalWindowManager实现，只是对WindowManagerImpl的封装调用。

private class LocalWindowManager implements WindowManager {

private final WindowManager mWindowManager;

LocalWindowManager(WindowManager wm) {

mWindowManager = wm;

}

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

//some code to check params here

mWindowManager.addView(view, params);

}

public void updateViewLayout(View view, ViewGroup.LayoutParams params) {

mWindowManager.updateViewLayout(view, params);

}

public final void removeView(View view) {

mWindowManager.removeView(view);

}

public final void removeViewImmediate(View view) {

mWindowManager.removeViewImmediate(view);

}

}

(2).Window.setWindowManager实现分析

public void setWindowManager(WindowManager wm, IBinder appToken, String appName) {

if (wm == null) {

wm = WindowManagerImpl.getDefault();

}

mWindowManager = new LocalWindowManager(wm);

}

四。回调Activity的onCreate方法。

(1). ActivityThread.java

private final Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {

mInstrumentation.callActivityOnCreate(activity, r.state);

}

(2). Instrumentation.java

public void callActivityOnCreate(Activity activity, Bundle icicle) {

activity.onCreate(icicle);

}

五。Activity中setContentView(int layout)分析

Activity.java

public void setContentView(int layoutResID) {

getWindow().setContentView(layoutResID);

}

public Window getWindow() {

return mWindow; //mWindow = PolicyManager.makeNewWindow(this);

}

六。Window中setContentView(int layout)分析

(1)PhoneWindow.java //因为Window是个abstract class， mWindow实际上是一个PhoneWindow对象

public void setContentView(int layoutResID) {

if (mContentParent == null) {

installDecor();

} else {

mContentParent.removeAllViews();

}

mLayoutInflater.inflate(layoutResID, mContentParent);

final Callback cb = getCallback();

if (cb != null) {

cb.onContentChanged();

}

}

(2) installDecor()分析 //PhoneWindow.java中

private void installDecor() {

if (mDecor == null) {

mDecor = generateDecor();

}

if (mContentParent == null) {

mContentParent = generateLayout(mDecor);

}

}

mDecor： class DecorView extends FrameLayout

mContentParent： class ViewGroup

(3)generateDecor()分析

protected DecorView generateDecor() {

return new DecorView(getContext(), -1);

}

DecorView:继承自FrameLayout，可以理解成窗口修饰，这个窗口修饰可以有各种style，比如标题栏，显示进度条等。常见的窗口修饰的layout路径为：frameworks/base/core/res/res/layout，比如R.layout.dialog_title_icons, R.layout.screen_title_icons.

(4)generateLayout()分析

protected ViewGroup generateLayout(DecorView decor) {

// Inflate the window decor.

int layoutResource;

if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {

if (mIsFloating) {

layoutResource = com.android.internal.R.layout.dialog_title_icons;

} else {

layoutResource = com.android.internal.R.layout.screen_title_icons;

}

} else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0) {

layoutResource = com.android.internal.R.layout.screen_progress;

} else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {

if (mIsFloating) {

layoutResource = com.android.internal.R.layout.dialog_custom_title;

} else {

layoutResource = com.android.internal.R.layout.screen_custom_title;

}

} else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {

if (mIsFloating) {

layoutResource = com.android.internal.R.layout.dialog_title;

} else {

layoutResource = com.android.internal.R.layout.screen_title;

}

} else {

layoutResource = com.android.internal.R.layout.screen_simple;

}

View in = mLayoutInflater.inflate(layoutResource, null);

decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));

ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);

if (contentParent == null) {

throw new RuntimeException("Window couldn't find content container view");

}

return contentParent;

}

DecorView的样式的定义：第一种是在Activity中onCreate中调用requestFeature（）。另一种是在AndroidManifest.xml中配置android:theme="xxx".

DecorView添加View：generateLayout的前部分代码，就是确定DecorView的样式，然后inflate这个layout文件，再调用DecorView.addView()添加到DecorView上。

mContentParent赋值：窗口修饰的layout中必须有一个FrameLayout，id为ID_ANDROID_CONTENT（实际上id=content），将这个FrameLayout赋值给mContentParent。

(5)添加窗口内容到mContentParent。

mLayoutInflater.inflate(layoutResID, mContentParent);

将activity传入的layoutRes添加到窗口装饰中。

(6)Window.Callback回调

final Callback cb = getCallback(); //Activity实现了Window.Callback接口，并且在创建PhoneWindow后，调用mWindow.setCallback(this)

if (cb != null) {

cb.onContentChanged();

}

七。通知WmS，显示DecorView

Activity准备好后会通知AmS，AmS通过一些条件判断，回调Activity的makeVisible().

(1.) Activity.java

public void setVisible(boolean visible) {

if (mVisibleFromClient != visible) {

mVisibleFromClient = visible;

if (mVisibleFromServer) {

if (visible) makeVisible();

else mDecor.setVisibility(View.INVISIBLE);

}

}

}

void makeVisible() {

if (!mWindowAdded) {

ViewManager wm = getWindowManager();

wm.addView(mDecor, getWindow().getAttributes()); //通过WindowManager将DecorView添加到window。

mWindowAdded = true;

}

mDecor.setVisibility(View.VISIBLE);

}

public Window getWindow() {

return mWindow;

}

(2.) Window.java

public final WindowManager.LayoutParams getAttributes() {

return mWindowAttributes;

}

private final WindowManager.LayoutParams mWindowAttributes =

new WindowManager.LayoutParams();

(3.) WindowManager.LayoutParams

public LayoutParams() {

super(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

type = TYPE_APPLICATION;

format = PixelFormat.OPAQUE;

}

(4.)Window.LocalWindowManager

wm.addView(mDecor, getWindow().getAttributes())分析

这个wm是LocalWindowManager，是对WindowManagerImpl的封装，目地是对params进行一些校验后，再调用WindowManagerImpl的addView。

校验params：

if (wp.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&

wp.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {

} else {

}

八。WindowManagerImpl.addView分析

方法：addView(View view, ViewGroup.LayoutParams params, boolean nest)；

class WindowManagerImpl extends WindowManager， interface WindowManager extends ViewManager

3个成员变量：

private View[] mViews;//每个view对象都将成为WmS所认为的一个窗口

private ViewRoot[] mRoots;//每个view对应一个ViewRoot

private WindowManager.LayoutParams[] mParams;//对应mViews的每个view的param

(1.)检查view是否已经添加过，不允许重复添加

int index = findViewLocked(view, false);

if (index >= 0) {

if (!nest) {

throw new IllegalStateException("View " + view

+ " has already been added to the window manager.");

}

root = mRoots[index];

root.mAddNesting++;

// Update layout parameters.

view.setLayoutParams(wparams);

root.setLayoutParams(wparams, true);

return;

}

(2.)检查窗口类型是否为sub window。如果是，则找到它的父窗口，并保存在临时变量panelParentView中，为下面调用ViewRoot的setView使用。

if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&

wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {

final int count = mViews != null ? mViews.length : 0;

for (int i=0; i<count; i++) {

if (mRoots[i].mWindow.asBinder() == wparams.token) {

panelParentView = mViews[i];

}

}

}

(3.)创建一个新的ViewRoot，上文说过每个view都对应一个ViewRoot。

root = new ViewRoot(view.getContext());

root.mAddNesting = 1;

ViewRoot的构造方法：

public ViewRoot(Context context) {

super();

// Initialize the statics when this class is first instantiated. This is

// done here instead of in the static block because Zygote does not

// allow the spawning of threads.

getWindowSession(context.getMainLooper()); //init static IWindowSession sWindowSession;

mThread = Thread.currentThread();

mLocation = new WindowLeaked(null);

mLocation.fillInStackTrace();

mWidth = -1;

mHeight = -1;

mDirty = new Rect();

mTempRect = new Rect();

mVisRect = new Rect();

mWinFrame = new Rect();

mWindow = new W(this, context); // class W extends IWindow.Stub

mInputMethodCallback = new InputMethodCallback(this);

mViewVisibility = View.GONE;

mTransparentRegion = new Region();

mPreviousTransparentRegion = new Region();

mFirst = true; // true for the first time the view is added

mAdded = false;

mAttachInfo = new View.AttachInfo(sWindowSession, mWindow, this, this);

mViewConfiguration = ViewConfiguration.get(context);

mDensity = context.getResources().getDisplayMetrics().densityDpi;

}

(4.)将view，root和param添加到上面的3个数组中。

if (mViews == null) {

index = 1;

mViews = new View[1];

mRoots = new ViewRoot[1];

mParams = new WindowManager.LayoutParams[1];

} else {

index = mViews.length + 1;

Object[] old = mViews; //保存原来的数组

mViews = new View[index]; //新建一个数组，长度+1

System.arraycopy(old, 0, mViews, 0, index-1); //将原来的数组copy到新建的数组中

old = mRoots;

mRoots = new ViewRoot[index];

System.arraycopy(old, 0, mRoots, 0, index-1);

old = mParams;

mParams = new WindowManager.LayoutParams[index];

System.arraycopy(old, 0, mParams, 0, index-1);

}

index--;

mViews[index] = view;

mRoots[index] = root;

mParams[index] = wparams;

(5.)调用ViewRoot的setView方法，完成最后的添加工作。

九。ViewRoot的setView分析

参数意义：

view： WindowManagerImpl中mViews数组中的元素，也就是新建的窗口界面

attrs：窗口参数，描述窗口的风格，大小，位置。attrs中的token变量指明了该窗口和activity的关系。

panelParentView：view的父窗口

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

synchronized (this) {

if (mView == null) {

mView = view;//给成员变量赋值。

mWindowAttributes.copyFrom(attrs);//给成员变量赋值。

attrs = mWindowAttributes;//给成员变量赋值。

………………………………

mSoftInputMode = attrs.softInputMode;//给成员变量赋值。

mWindowAttributesChanged = true;//给成员变量赋值。

mAttachInfo.mRootView = view;//给成员变量赋值。

if (panelParentView != null) {

mAttachInfo.mPanelParentWindowToken

= panelParentView.getApplicationWindowToken();

}

………………………………

requestLayout(); //发出重绘请求，使该 在相应消息前变的可见

………………………………

try {

//通知WmS，添加窗口

res = sWindowSession.add(mWindow, mWindowAttributes,

getHostVisibility(), mAttachInfo.mContentInsets,

mInputChannel);

} catch (RemoteException e) {

}

}

}

}

十。sWindowSession.add分析

（1）IWindowSession是一个aidl接口，实现类是在WmS中：class Session extends IWindowSession.Stub

（2）sWindowSession的初始化： //static IWindowSession sWindowSession;

public static IWindowSession getWindowSession(Looper mainLooper) {

synchronized (mStaticInit) {

if (!mInitialized) {

try {

InputMethodManager imm = InputMethodManager.getInstance(mainLooper);

sWindowSession = IWindowManager.Stub.asInterface(

ServiceManager.getService("window")) //先获得WmS

.openSession(imm.getClient(), imm.getInputContext()); //再通过WmS获取分配的IWindowSession

mInitialized = true;

} catch (RemoteException e) {

}

}

return sWindowSession;

}

}

（3）sWindowSession为static，WmS为每个进程只分配1个。调用sWindowSession.add是app请求WmS添加窗口的唯一入口。

总结：至此，从客户端的角度讲，已经完成了窗口创建的全部工作。