http://blog.csdn.net/ljsbuct/article/details/7094580
1. 入口。
以前一直都说Activity的人口是onCreate方法。其实android上一个应用的入口，应该是ActivityThread。和普通的java类一样，入口是一个main方法。
public static final void main(String[] args) {
SamplingProfilerIntegration.start();
……
Looper.prepareMainLooper();
if (sMainThreadHandler == null) {
sMainThreadHandler = new Handler();
}
ActivityThread thread = new ActivityThread();
thread.attach(false);
……
Looper.loop();
……
thread.detach();
……
Slog.i(TAG, "Main thread of " + name + " is now exiting");
}
下面仔细分析一下这个main方法。
2.Looper.prepareMainLooper();
ActivityThread其实就是我们经常说的UI
thread，也就是主线程。我们都知道主线程可以使用Handler进行异步通信，因为主线程中已经创建了Looper，而这个Looper就是在这里
创建的。如果其他线程需要使用Handler通信，就要自己去创建Looper。
3. sMainThreadHandler = new Handler();
创建一个Handler。
4. ActivityThread thread = new ActivityThread();
创建ActivityThread 对象。
ActivityThread 有几个比较重要的成员变量，会在创建ActivityThread对象时初始化。
（1）final ApplicationThread mAppThread = new ApplicationThread();
ApplicationThread继承自ApplicationThreadNative，
而ApplicationThreadNative又继承自Binder并实现了IApplicationThread接口。
IApplicationThread继承自IInterface。这是一个很明显的binder结构，用于于Ams通信。
IApplicationThread接口定义了对一个程序（linux的进程）操作的接口。ApplicationThread通过binder与
Ams通信，并将Ams的调用，通过下面的H类（也就是Hnalder）将消息发送到消息队列，然后进行相应的操作，入activity的start，
stop。
（2）final H mH = new H();
private final class H extends Handler
mH负责处理ApplicationThread发送到消息队列的消息，例如：
public void handleMessage(Message msg) {
if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + msg.what);
switch (msg.what) {
case LAUNCH_ACTIVITY: {
ActivityClientRecord r = (ActivityClientRecord)msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo);
handleLaunchActivity(r, null);
} break;
5. handleLaunchActivity(r, null);
从名字中就可以看出，这里就将进行启动activity的工作了。
方法中主要调用了这一句：
Activity a = performLaunchActivity(r, customIntent);
6. performLaunchActivity（）
进行了一些初始化和赋值操作后，创建activity。
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
然后调用：
mInstrumentation.callActivityOnCreate(activity, r.state);
这一句就会调用到acitivity的onCreate方法了，就进入了大多数应用开发的入口了。
http://blog.csdn.net/ljsbuct/article/details/7094575
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。