文章一開始我要对前面一篇文章做点补充
相信大家都知道View有两个方法。
public boolean post(Runnable action)
public boolean postDelayed(Runnable action, long delayMillis) {这两个方法也能够实现对View的包装（实现延时发送消息和更新UI）那么它和Handler有什么差别呢下面给出源代码。
/**
* <p>Causes the Runnable to be added to the message queue, to be run
* after the specified amount of time elapses.
* The runnable will be run on the user interface thread.</p>
*<BR>使Runnable被加入到消息队列。执行将执行在用户界面线程。@param行动的执行将被执行。
* @返回返回true假设执行成功放置到
*消息队列。
执行失败将返回False。一般是由于
* looper处理消息队列退出。
* @param action The Runnable that will be executed.
* @param delayMillis The delay (in milliseconds) until the Runnable
* will be executed.
*
* @return true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the Runnable will be processed --
* if the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*
* @see #post
* @see #removeCallbacks
*/
public boolean postDelayed(Runnable action, long delayMillis) {
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
return attachInfo.mHandler.postDelayed(action, delayMillis);
}
// Assume that post will succeed later
ViewRootImpl.getRunQueue().postDelayed(action, delayMillis);
return true;
}
/**
* <p>Causes the Runnable to be added to the message queue, to be run
* after the specified amount of time elapses.
* The runnable will be run on the user interface thread.</p>
*使Runnable被加入到消息队列，能够执行在指定时间的流逝之后
* @param action The Runnable that will be executed.
* @param delayMillis The delay (in milliseconds) until the Runnable
* will be executed.
*
* @return true if the Runnable was successfully placed in to the
* message queue. Returns false on failure, usually because the
* looper processing the message queue is exiting. Note that a
* result of true does not mean the Runnable will be processed --
* if the looper is quit before the delivery time of the message
* occurs then the message will be dropped.
*
* @see #post
* @see #removeCallbacks
*/
public boolean postDelayed(Runnable action, long delayMillis) {
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
return attachInfo.mHandler.postDelayed(action, delayMillis);
}
// Assume that post will succeed later
ViewRootImpl.getRunQueue().postDelayed(action, delayMillis);
return true;
}关键的凝视我也进行的翻译。相信大家如今已经明确了。
在post(Runnable action)方法里。View获得当前线程（即UI线程）的Handler。然后将action对象post到Handler里。在Handler里，它将传递过来的action对象包装成一个Message（Message的callback为action），然后将其投入UI线程的消息循环中。在Handler再次处理该Message时，有一条分支（未解释的那条）就是为它所设，直接调用runnable的run方法。而此时，已经路由到UI线程里，因此。我们能够毫无顾虑的来更新UI。
这样的情况下。由于不是在新的线程中使用，所以千万别做复杂的计算逻辑。更不能进行耗时操作了
那大家又会问什么是ViewRootImpl？这特么又是什么鬼，这里给大家解说一下。我们从最基础的讲起。
相信大家都知道我们通过调用setContentView（int layoutResID）把xml文件载入到当前Activity上的。
那我们就从setContentView讲起。
public void setContentView(int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}setContentView方法实现非常easy，里面调用两个方法，我们这里分析第一个方法：
getWindow()得到一个Window对象 mWindow ，Window是一个抽象类，用来描写叙述Activity视图最顶端的窗体显示和行为操作。Window是一个抽象类。那么里面的setContentView(layoutResID)是一个抽象方法。并没有具体的实现。既然Window是一个抽象类，那么在Activity里面就有一个Window抽象类的实现。们查找代码发现 mWindow对象赋值方法例如以下。
mWindow = PolicyManager.makeNewWindow(this);继续看看 PolicyManager类
public final class More PolicyManager {
30 private static final String POLICY_IMPL_CLASS_NAME =
31 "com.android.internal.policy.impl.Policy";
32
33 private static final IPolicy sPolicy;
34
35 static {
36 // Pull in the actual implementation of the policy at run-time
37 try {
38 Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME);
39 sPolicy = (IPolicy)policyClass.newInstance();
40 } catch (ClassNotFoundException ex) {
41 throw new RuntimeException(
42 POLICY_IMPL_CLASS_NAME + " could not be loaded", ex);
43 } catch (InstantiationException ex) {
44 throw new RuntimeException(
45 POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
46 } catch (IllegalAccessException ex) {
47 throw new RuntimeException(
48 POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
49 }
50 }
51
52 // Cannot instantiate this class
53 private More PolicyManager() {}
54
55 // The static methods to spawn new policy-specific objects
56 public static Window More makeNewWindow(Context context) {
57 return sPolicy.makeNewWindow(context);
58 }通过分析我们发现sPolicy对象是有第 38。39行通过径”com.android.internal.policy.impl.Policy“生成的（通过反射拿到类的对象而且实例化）重点57，
public Window makeNewWindow(Context context) {
return new PhoneWindow(context);
}由此可见，我们最终找到Activity类中的 mWindow对象的实现类了。就是PhoneWindow类。
可能又会有些童学问什么是反射呢？what Fuck，要是特么这样扯下去，预计三天三夜也扯不完，等这篇写完后，会专一分一篇来解说Java的反射机制。
到PhoneWindow类发现了setContentView方法的实现也在这个类里面了
@Override
public void setContentView(int layoutResID) {
// Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. Do not check the feature
// before this happens.
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);
}
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}首先推断mContentParent是否为null，mContentParent是什么呢？接下来会分析，一開始条件成立，进入installDecor()方法
到installDecor()方法里，实现例如以下：
private void installDecor() {
if (mDecor == null) {
mDecor = generateDecor();
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);
// Set up decor part of UI to ignore fitsSystemWindows if appropriate.
mDecor.makeOptionalFitsSystemWindows();
final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(
R.id.decor_content_parent);
if (decorContentParent != null) {
mDecorContentParent = decorContentParent;
mDecorContentParent.setWindowCallback(getCallback());
if (mDecorContentParent.getTitle() == null) {
mDecorContentParent.setWindowTitle(mTitle);
}
final int localFeatures = getLocalFeatures();
for (int i = 0; i < FEATURE_MAX; i++) {
if ((localFeatures & (1 << i)) != 0) {
mDecorContentParent.initFeature(i);
}
}
mDecorContentParent.setUiOptions(mUiOptions);
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) != 0 ||
(mIconRes != 0 && !mDecorContentParent.hasIcon())) {
mDecorContentParent.setIcon(mIconRes);
} else if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) == 0 &&
mIconRes == 0 && !mDecorContentParent.hasIcon()) {
mDecorContentParent.setIcon(
getContext().getPackageManager().getDefaultActivityIcon());
mResourcesSetFlags |= FLAG_RESOURCE_SET_ICON_FALLBACK;
}
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_LOGO) != 0 ||
(mLogoRes != 0 && !mDecorContentParent.hasLogo())) {
mDecorContentParent.setLogo(mLogoRes);
}
// Invalidate if the panel menu hasn't been created before this.
// Panel menu invalidation is deferred avoiding application onCreateOptionsMenu
// being called in the middle of onCreate or similar.
// A pending invalidation will typically be resolved before the posted message
// would run normally in order to satisfy instance state restoration.
PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false);
if (!isDestroyed() && (st == null || st.menu == null)) {
invalidatePanelMenu(FEATURE_ACTION_BAR);
}
} else {
mTitleView = (TextView)findViewById(R.id.title);
if (mTitleView != null) {
mTitleView.setLayoutDirection(mDecor.getLayoutDirection());
if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {
View titleContainer = findViewById(
R.id.title_container);
if (titleContainer != null) {
titleContainer.setVisibility(View.GONE);
} else {
mTitleView.setVisibility(View.GONE);
}
if (mContentParent instanceof FrameLayout) {
((FrameLayout)mContentParent).setForeground(null);
}
} else {
mTitleView.setText(mTitle);
}
}
}
if (mDecor.getBackground() == null && mBackgroundFallbackResource != 0) {
mDecor.setBackgroundFallback(mBackgroundFallbackResource);
}
// Only inflate or create a new TransitionManager if the caller hasn't
// already set a custom one.
if (hasFeature(FEATURE_ACTIVITY_TRANSITIONS)) {
if (mTransitionManager == null) {
final int transitionRes = getWindowStyle().getResourceId(
R.styleable.Window_windowContentTransitionManager,
0);
if (transitionRes != 0) {
final TransitionInflater inflater = TransitionInflater.from(getContext());
mTransitionManager = inflater.inflateTransitionManager(transitionRes,
mContentParent);
} else {
mTransitionManager = new TransitionManager();
}
}
mEnterTransition = getTransition(mEnterTransition, null,
R.styleable.Window_windowEnterTransition);
mReturnTransition = getTransition(mReturnTransition, USE_DEFAULT_TRANSITION,
R.styleable.Window_windowReturnTransition);
mExitTransition = getTransition(mExitTransition, null,
R.styleable.Window_windowExitTransition);
mReenterTransition = getTransition(mReenterTransition, USE_DEFAULT_TRANSITION,
R.styleable.Window_windowReenterTransition);
mSharedElementEnterTransition = getTransition(mSharedElementEnterTransition, null,
R.styleable.Window_windowSharedElementEnterTransition);
mSharedElementReturnTransition = getTransition(mSharedElementReturnTransition,
USE_DEFAULT_TRANSITION,
R.styleable.Window_windowSharedElementReturnTransition);
mSharedElementExitTransition = getTransition(mSharedElementExitTransition, null,
R.styleable.Window_windowSharedElementExitTransition);
mSharedElementReenterTransition = getTransition(mSharedElementReenterTransition,
USE_DEFAULT_TRANSITION,
R.styleable.Window_windowSharedElementReenterTransition);
if (mAllowEnterTransitionOverlap == null) {
mAllowEnterTransitionOverlap = getWindowStyle().getBoolean(
R.styleable.Window_windowAllowEnterTransitionOverlap, true);
}
if (mAllowReturnTransitionOverlap == null) {
mAllowReturnTransitionOverlap = getWindowStyle().getBoolean(
R.styleable.Window_windowAllowReturnTransitionOverlap, true);
}
if (mBackgroundFadeDurationMillis < 0) {
mBackgroundFadeDurationMillis = getWindowStyle().getInteger(
R.styleable.Window_windowTransitionBackgroundFadeDuration,
DEFAULT_BACKGROUND_FADE_DURATION_MS);
}
if (mSharedElementsUseOverlay == null) {
mSharedElementsUseOverlay = getWindowStyle().getBoolean(
R.styleable.Window_windowSharedElementsUseOverlay, true);
}
}
}
}重点在代码的第 3 行我们看到 mDecor = generateDecor();方法调用，继续跳进 generateDecor()方法：
protected DecorView generateDecor() {
return new DecorView(getContext(), -1);
}这里生成一个DecorView对象，DecorView是PhoneWindow类的内部类，继承自FrameLayout。到眼下为止。setContentView方法里生成一个FrameLayout类型的DecorView组件。
继续分析代码，看第 11 行：
mContentParent = generateLayout(mDecor);把 DecorView 对象 mDecor 作为參数传递给 generateLayout方法得到 mContentParent。generateLayout()方法中的代码实现例如以下：
protected ViewGroup generateLayout(DecorView decor) {
// Apply data from current theme.
TypedArray a = getWindowStyle();
.........
/**下面这些是Activity 窗体属性特征的设置*/
//窗体是否浮动，一般用于Dialog窗体是否浮动：是否显示在布局的正中间。
mIsFloating = a.getBoolean(R.styleable.Window_windowIsFloating, false);
int flagsToUpdate = (FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR)
& (~getForcedWindowFlags());
if (mIsFloating) {
setLayout(WRAP_CONTENT, WRAP_CONTENT);
setFlags(0, flagsToUpdate);
} else {
setFlags(FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR, flagsToUpdate);
}
//设置窗体是否支持标题栏。隐藏显示标题栏操作在此处。
if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) {
requestFeature(FEATURE_NO_TITLE);
} else if (a.getBoolean(R.styleable.Window_windowActionBar, false)) {
// Don't allow an action bar if there is no title.
requestFeature(FEATURE_ACTION_BAR);
}
//ActionBar导航栏是否不占布局空间叠加显示在当前窗体之上。
if (a.getBoolean(R.styleable.Window_windowActionBarOverlay, false)) {
requestFeature(FEATURE_ACTION_BAR_OVERLAY);
}
if (a.getBoolean(R.styleable.Window_windowActionModeOverlay, false)) {
requestFeature(FEATURE_ACTION_MODE_OVERLAY);
}
if (a.getBoolean(R.styleable.Window_windowSwipeToDismiss, false)) {
requestFeature(FEATURE_SWIPE_TO_DISMISS);
}
//当前Activity是否支持全屏
if (a.getBoolean(R.styleable.Window_windowFullscreen, false)) {
setFlags(FLAG_FULLSCREEN, FLAG_FULLSCREEN & (~getForcedWindowFlags()));
}
................
//设置状态栏的颜色
if (!mForcedStatusBarColor) {
mStatusBarColor = a.getColor(R.styleable.Window_statusBarColor, 0xFF000000);
}
//设置导航栏的颜色
if (!mForcedNavigationBarColor) {
mNavigationBarColor = a.getColor(R.styleable.Window_navigationBarColor, 0xFF000000);
}
if (mAlwaysReadCloseOnTouchAttr || getContext().getApplicationInfo().targetSdkVersion
>= android.os.Build.VERSION_CODES.HONEYCOMB) {
if (a.getBoolean(
R.styleable.Window_windowCloseOnTouchOutside,
false)) {
setCloseOnTouchOutsideIfNotSet(true);
}
}
WindowManager.LayoutParams params = getAttributes();
//设置输入法的状态
if (!hasSoftInputMode()) {
params.softInputMode = a.getInt(
R.styleable.Window_windowSoftInputMode,
params.softInputMode);
}
if (a.getBoolean(R.styleable.Window_backgroundDimEnabled,
mIsFloating)) {
/* All dialogs should have the window dimmed */
if ((getForcedWindowFlags()&WindowManager.LayoutParams.FLAG_DIM_BEHIND) == 0) {
params.flags |= WindowManager.LayoutParams.FLAG_DIM_BEHIND;
}
if (!haveDimAmount()) {
params.dimAmount = a.getFloat(
android.R.styleable.Window_backgroundDimAmount, 0.5f);
}
}
//设置当前Activity的出现动画效果
if (params.windowAnimations == 0) {
params.windowAnimations = a.getResourceId(
R.styleable.Window_windowAnimationStyle, 0);
}
// The rest are only done if this window is not embedded; otherwise,
// the values are inherited from our container.
if (getContainer() == null) {
if (mBackgroundDrawable == null) {
if (mBackgroundResource == 0) {
mBackgroundResource = a.getResourceId(
R.styleable.Window_windowBackground, 0);
}
if (mFrameResource == 0) {
mFrameResource = a.getResourceId(R.styleable.Window_windowFrame, 0);
}
mBackgroundFallbackResource = a.getResourceId(
R.styleable.Window_windowBackgroundFallback, 0);
if (false) {
System.out.println("Background: "
+ Integer.toHexString(mBackgroundResource) + " Frame: "
+ Integer.toHexString(mFrameResource));
}
}
mElevation = a.getDimension(R.styleable.Window_windowElevation, 0);
mClipToOutline = a.getBoolean(R.styleable.Window_windowClipToOutline, false);
mTextColor = a.getColor(R.styleable.Window_textColor, Color.TRANSPARENT);
}
//下面代码为当前Activity窗体加入 decor根布局。
// Inflate the window decor.
int layoutResource;
int features = getLocalFeatures();
// System.out.println("Features: 0x" + Integer.toHexString(features));
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
layoutResource = R.layout.screen_swipe_dismiss;
} else if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
R.attr.dialogTitleIconsDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = R.layout.screen_title_icons;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
// System.out.println("Title Icons!");
} else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0
&& (features & (1 << FEATURE_ACTION_BAR)) == 0) {
// Special case for a window with only a progress bar (and title).
// XXX Need to have a no-title version of embedded windows.
layoutResource = R.layout.screen_progress;
// System.out.println("Progress!");
} else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {
// Special case for a window with a custom title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
R.attr.dialogCustomTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = R.layout.screen_custom_title;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
} else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {
// If no other features and not embedded, only need a title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
R.attr.dialogTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {
layoutResource = a.getResourceId(
R.styleable.Window_windowActionBarFullscreenDecorLayout,
R.layout.screen_action_bar);
} else {
layoutResource = R.layout.screen_title;
}
// System.out.println("Title!");
} else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {
layoutResource = R.layout.screen_simple_overlay_action_mode;
} else {
// Embedded, so no decoration is needed.
layoutResource = R.layout.screen_simple;
// System.out.println("Simple!");
}
mDecor.startChanging();
//通过布局加入器LayoutInflater获取layoutResource布局，
View in = mLayoutInflater.inflate(layoutResource, null);
//将XML资源为layoutResource的布局加入到decor容器里面。至此PhoneWindow 内部类DecorView就加入了之布局
decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
mContentRoot = (ViewGroup) in;
//此处非常重要。通过findViewById找到 contentParent容器，也是该方法的返回值。
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view");
}
if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
ProgressBar progress = getCircularProgressBar(false);
if (progress != null) {
progress.setIndeterminate(true);
}
}
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
registerSwipeCallbacks();
}
// Remaining setup -- of background and title -- that only applies
// to top-level windows.
//下面代码设置Activity窗体的背景，标题等
if (getContainer() == null) {
final Drawable background;
if (mBackgroundResource != 0) {
background = getContext().getDrawable(mBackgroundResource);
} else {
background = mBackgroundDrawable;
}
mDecor.setWindowBackground(background);
final Drawable frame;
if (mFrameResource != 0) {
frame = getContext().getDrawable(mFrameResource);
} else {
frame = null;
}
mDecor.setWindowFrame(frame);
mDecor.setElevation(mElevation);
mDecor.setClipToOutline(mClipToOutline);
if (mTitle != null) {
setTitle(mTitle);
}
if (mTitleColor == 0) {
mTitleColor = mTextColor;
}
setTitleColor(mTitleColor);
}
mDecor.finishChanging();
return contentParent;
}
以上代码代比較复杂。主要做了下面几件事情。
从第 8 行到第110行，主要是初始化窗体的特征。是否显示标题栏。是否全屏，是否支持ActionBar浮动等等。
第112-187行。主要是给容器DecorView加入id为layoutResource布局的根布局。待会分析layoutResource布局。
第178行。通过LayoutInflater 将xml布局转换成VIEW.
第180行将找到的View加入到DecorView根布局其中。
第184行，从根布局中找到id为R.id.content的 contentParent 容器。也就是当前方法的返回值。
接下来，看看 id为layoutResource的布局究竟实现了什么？我们来看看171行的R.layout.screen_simple;资源
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:orientation="vertical">
<ViewStub android:id="@+id/action_mode_bar_stub"
android:inflatedId="@+id/action_mode_bar"
android:layout="@layout/action_mode_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="?attr/actionBarTheme" />
<FrameLayout
android:id="@android:id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:foregroundInsidePadding="false"
android:foregroundGravity="fill_horizontal|top"
android:foreground="?android:attr/windowContentOverlay"
/>
</LinearLayout>原来我们的DecorView根布局里面加入了相似上面的布局，线性布局LinearLaout里包括两个组件，ViewStub是懒载入，默认不显示。FrameLayout是什么呢？看看id=content，就是我们184行找到的父容器 contentParent。那么这个父容器 contentParent有什么作用呢？
我们回到 Step4 的第 11行，mContentParent = generateLayout(mDecor); 获得 父容器 mContentParent。我们再次回到 Step3步的第17行， mLayoutInflater.inflate(layoutResID, mContentParent); 这里通过LayoutInflater将 setContentView（layoutResID）传进来的布局id载入到 父容器mContentParent中，至此。setContentView就将布局加入到Activity里面了。
如今我们来梳理一下流程：
Activity setContentView—>Window setContentView—>PhoneWindow setContentView—->PhoneWindow installDecor—–>PhoneWindow generateLayout——>PhoneWindow mLayoutInflater.inflate(layoutResID, mContentParent);Activity 类中有一个Window抽象类的实现PhoneWindow类，该类中有个内部类DecorView。继承自FrameLayout。在DecorView容器中加入了根布局。根布局中包括了一个id为 contnet的FrameLayout 内容布局。我们的Activity载入的布局xml最后加入到 id为content的FrameLayout布局其中了
1.关于requestWindowFeature(Window.FEATURE_NO_TITLE); 去除标题栏的疑问，假设你自己的xxxActivity是继承自Activity。那么恭喜你使用以上方法能够去除标题栏，假设你自己的xxxActivity是继承自AppCompatActivity或者ActionBarActivity，那么非常遗憾告诉你，此次系统默认的标题栏已经在主题中去除，此时显示的标题栏是ActionBar导航栏，假设须要去除导航栏，你能够通过例如以下代码：getSupportActionBar().hide();来隐藏导航栏。
2.requestWindowFeature(Window.FEATURE_NO_TITLE);方法须要在 setContentView方法之前使用。由上面 Step5分析可得。设置Activity Window 特征是在setContentView方法中设置的，因此，假设须要改变Activity Window窗体特征，须要在setContentView方法之前。
事实上这里有疑问？？？为什么设置全屏的方法getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
关于mLayoutInflater.inflate我会在下篇给大家具体解说的。
太特么累了，我要喝脉动。
