Activity的创建和显示以及源码分析记录
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Tips:此源码分析基于Android 4.2
先来看看一个Activity上的UI控件结构：
图1-1 Activity中的UI组件结构
好了现在开始分析。。。。。。
一、Activity的创建
了解android的zygote分裂你会知道，每个APP都是zygote的子进程，而他的入口函数是ActivityThread类中的main函数。其中有一个handleLaucherActivity函数，这里就是
创建Activity的地方。
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) { // If we are getting ready to gc after going to the background, well // we are back active so skip it. unscheduleGcIdler(); if (r.profileFd != null) { mProfiler.setProfiler(r.profileFile, r.profileFd); mProfiler.startProfiling(); mProfiler.autoStopProfiler = r.autoStopProfiler; } // Make sure we are running with the most recent config. handleConfigurationChanged(null, null); if (localLOGV) Slog.v( TAG, "Handling launch of " + r); //重点一 Activity a = performLaunchActivity(r, customIntent); if (a != null) { r.createdConfig = new Configuration(mConfiguration); Bundle oldState = r.state; // 重点二 handleResumeActivity(r.token, false, r.isForward, !r.activity.mFinished && !r.startsNotResumed); } 后面代码省略 ...... }这里已经标出了两个重点的函数
先来看看第一个performLauncherActivity
这个函数返回一个activity,可见activity确实在这里创建了，先上代码
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) { ...... Activity activity = null; try { java.lang.ClassLoader cl = r.packageInfo.getClassLoader(); //正真创建activity的地方 activity = mInstrumentation.newActivity( cl, component.getClassName(), r.intent); StrictMode.incrementExpectedActivityCount(activity.getClass()); 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); } } ...... if (activity != null) { Context appContext = createBaseContextForActivity(r, activity); CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager()); Configuration config = new Configuration(mCompatConfiguration); if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity " + r.activityInfo.name + " with config " + config); //又是一个重点，暂且先不分析，，， activity.attach(appContext, this, getInstrumentation(), r.token, r.ident, app, r.intent, r.activityInfo, title, r.parent, r.embeddedID, r.lastNonConfigurationInstances, config); if (customIntent != null) { activity.mIntent = customIntent; } r.lastNonConfigurationInstances = null; activity.mStartedActivity = false; int theme = r.activityInfo.getThemeResource(); if (theme != 0) { activity.setTheme(theme); } activity.mCalled = false; //这里回调了Activity的OnCreate mInstrumentation.callActivityOnCreate(activity, r.state); if (!activity.mCalled) { throw new SuperNotCalledException( "Activity " + r.intent.getComponent().toShortString() + " did not call through to super.onCreate()"); } r.activity = activity; r.stopped = true; if (!r.activity.mFinished) { activity.performStart(); r.stopped = false; } if (!r.activity.mFinished) { if (r.state != null) { mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state); } } if (!r.activity.mFinished) { activity.mCalled = false; mInstrumentation.callActivityOnPostCreate(activity, r.state); if (!activity.mCalled) { throw new SuperNotCalledException( "Activity " + r.intent.getComponent().toShortString() + " did not call through to super.onPostCreate()"); } } } ...... return activity;}这里贴上了关键的代码，由此可见performLauncherActivity函数主要做了两件重要的事情，创建了Activity以及回调了OnCreate。
这里看出他是利用了Java的反射机制根据类名创建了一个Activity
接下来再来看下第二个函数handleResumeActivity,什么都不说先看代码：
final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward, boolean reallyResume) { ...... if (r.window == null && !a.mFinished && willBeVisible) { r.window = r.activity.getWindow(); View decor = r.window.getDecorView(); decor.setVisibility(View.INVISIBLE); ViewManager wm = a.getWindowManager(); WindowManager.LayoutParams l = r.window.getAttributes(); a.mDecor = decor; l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION; l.softInputMode |= forwardBit; if (a.mVisibleFromClient) { a.mWindowAdded = true; //关键函数 wm.addView(decor, l); } // If the window has already been added, but during resume // we started another activity, then don't yet make the // window visible. } ....... } 到了这里可以看到多了两个比较重要的对象View, ViewManager, 随后decor对象add到了ViewManager,那么这两个对象到底是什么呢？
getDectorView进去一看原来是Window类的一个抽象方法，那么到底是什么实现了他？
这就要看刚刚哪个Activity的attach函数了
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, NonConfigurationInstances lastNonConfigurationInstances, Configuration config) { attachBaseContext(context); mFragments.attachActivity(this, mContainer, null); //创建了一个mWindow,这是一个实现了Window抽象方法的对象 mWindow = PolicyManager.makeNewWindow(this); mWindow.setCallback(this); mWindow.getLayoutInflater().setPrivateFactory(this); ...... //创建了WindowManager mWindow.setWindowManager( (WindowManager)context.getSystemService(Context.WINDOW_SERVICE), mToken, mComponent.flattenToString(), (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0); if (mParent != null) { mWindow.setContainer(mParent.getWindow()); } mWindowManager = mWindow.getWindowManager(); mCurrentConfig = config; }在handleResumeActivity中的r.window = r.activity.getWindow();我们可以看出这里创建的mWindow给了r.window
public Window getWindow() { return mWindow; }创建mWindow时有出现了个PolicyManager,现在先看看这个是什么东西
public final class PolicyManager { 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 try { Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME); sPolicy = (IPolicy)policyClass.newInstance(); } catch (ClassNotFoundException ex) { throw new RuntimeException( POLICY_IMPL_CLASS_NAME + " could not be loaded", ex); } catch (InstantiationException ex) { throw new RuntimeException( POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex); } catch (IllegalAccessException ex) { throw new RuntimeException( POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex); } } // Cannot instantiate this class private PolicyManager() {} // The static methods to spawn new policy-specific objects public static Window makeNewWindow(Context context) { return sPolicy.makeNewWindow(context); } public static LayoutInflater makeNewLayoutInflater(Context context) { return sPolicy.makeNewLayoutInflater(context); } public static WindowManagerPolicy makeNewWindowManager() { return sPolicy.makeNewWindowManager(); } public static FallbackEventHandler makeNewFallbackEventHandler(Context context) { return sPolicy.makeNewFallbackEventHandler(context); }}从这里可以看出调用的PolicyManager.makeNewWindow(this)正真实现是在Policy中
public Window makeNewWindow(Context context) { return new PhoneWindow(context); }至此我们才发现所谓的mWindow其实是一个PhoneWindow对象现在我们在了看看正真实现getDecorView的PhoneWindow中获得的View到底是什么？
@Override public final View getDecorView() { if (mDecor == null) { installDecor(); } return mDecor; }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(); mTitleView = (TextView)findViewById(com.android.internal.R.id.title); ...... } ......}private final class DecorView extends FrameLayout implements RootViewSurfaceTaker
好了现在解决了我们第一个问题，View到底是什么？现在我们再来分析下ViewManager究竟是什么？
ViewManager wm = a.getWindowManager();
查看activity的getWindowManager以及attach方法我们会发现这正是attach方法中创建的WindowManager
public WindowManager getWindowManager() { return mWindowManager; }但是WindowManager只是一个公共的接口，我们还是得进入到attach中的mWindow.setWindowManager()中看看到底发生了什么？
public interface WindowManager extends ViewManager
public void setWindowManager(WindowManager wm, IBinder appToken, String appName, boolean hardwareAccelerated) { mAppToken = appToken; mAppName = appName; mHardwareAccelerated = hardwareAccelerated || SystemProperties.getBoolean(PROPERTY_HARDWARE_UI, false); if (wm == null) { wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE); } mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this); }public WindowManagerImpl createLocalWindowManager(Window parentWindow) { return new WindowManagerImpl(mDisplay, parentWindow); }到此我们终于解决了我们的第二个问题，哪个ViewManager其实是WindowManagerImpl
好了处理了这门多复杂的关系，我们先来总结下：
1、我们是分析到了handleResumeActivity这个函数,想弄清楚View跟ViewManager分别是什么？
2、之后我们返回去查看activity的attache函数，发现其中创建的mWindow跟mWindowManager其实是PhoneWindow与WindowManagerImpl.
3、我们再回到View与ViewManager的创建过程，发下其实View是在PhoneWindow中创建的DecorView而ViewManager正是mWindowManager(即WindowManagerImpl)，
在attach中调用Window的setWindowManager时将创建的WindowManagerImpl保存了起来。
经过这般分析再来看这张图：
图1-2 Window与WindowManager
好了，接下来我们继续来分析handleResumeActivity中另一个很关键的函数wm.addView(decor, l);
addView的正真实现实在frameworks\base\core\java\android\view\WindowManagerGlobal.java
public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (display == null) { throw new IllegalArgumentException("display must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params; if (parentWindow != null) { parentWindow.adjustLayoutParamsForSubWindow(wparams); } ViewRootImpl root; View panelParentView = null; synchronized (mLock) { // Start watching for system property changes. if (mSystemPropertyUpdater == null) { mSystemPropertyUpdater = new Runnable() { @Override public void run() { synchronized (mLock) { for (ViewRootImpl viewRoot : mRoots) { viewRoot.loadSystemProperties(); } } } }; SystemProperties.addChangeCallback(mSystemPropertyUpdater); } int index = findViewLocked(view, false); if (index >= 0) { throw new IllegalStateException("View " + view + " has already been added to the window manager."); } // If this is a panel window, then find the window it is being // attached to for future reference. 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]; } } } root = new ViewRootImpl(view.getContext(), display); view.setLayoutParams(wparams); if (mViews == null) { index = 1; mViews = new View[1]; mRoots = new ViewRootImpl[1]; mParams = new WindowManager.LayoutParams[1]; } else { index = mViews.length + 1; Object[] old = mViews; mViews = new View[index]; System.arraycopy(old, 0, mViews, 0, index-1); old = mRoots; mRoots = new ViewRootImpl[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; } // do this last because it fires off messages to start doing things try { root.setView(view, wparams, panelParentView); } catch (RuntimeException e) { // BadTokenException or InvalidDisplayException, clean up. synchronized (mLock) { final int index = findViewLocked(view, false); if (index >= 0) { removeViewLocked(index, true); } } throw e; } }这里有出现了一个新的对象ViewRootImpl以及调用了它的一个重要方法setView,现在我们就来分析下
public final class ViewRootImpl implements ViewParent, View.AttachInfo.Callbacks, HardwareRenderer.HardwareDrawCallbacks
查看ViewRootImpl的源码可以知道它里面包含了几个重要的成员对象(frameworks\base\core\java\android\view\ViewRootImpl.java)
有一个mSurface,他是Surface类型，而前面提到的UI都是在这上面绘画出来的，可以想象成一个画布
还有一个W类型的内部类，这个类将参与Binder通信
static class W extends IWindow.Stub
并且重写了handleMessage
我们接着看下ViewRootImpl的构造函数：
public ViewRootImpl(Context context, Display display) { super(); if (MEASURE_LATENCY) { if (lt == null) { lt = new LatencyTimer(100, 1000); } } // 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. mWindowSession = WindowManagerGlobal.getWindowSession(context.getMainLooper()); mDisplay = display; CompatibilityInfoHolder cih = display.getCompatibilityInfo(); mCompatibilityInfo = cih != null ? cih : new CompatibilityInfoHolder(); 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); ......}这里一个比较重要的函数是getWindowSession
public static IWindowSession getWindowSession(Looper mainLooper) { synchronized (WindowManagerGlobal.class) { if (sWindowSession == null) { try { InputMethodManager imm = InputMethodManager.getInstance(mainLooper); IWindowManager windowManager = getWindowManagerService(); sWindowSession = windowManager.openSession( imm.getClient(), imm.getInputContext()); float animatorScale = windowManager.getAnimationScale(2); ValueAnimator.setDurationScale(animatorScale); } catch (RemoteException e) { Log.e(TAG, "Failed to open window session", e); } } return sWindowSession; } }这里又是一个Binder机制的跨进程调用，可以看出ViewRootImpl还和WindowManagerServer有着密切的联系，这里就不讨论了。。。。
现在我们来看下setView中的调用的一个重要方法
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) { ...... // Schedule the first layout -before- adding to the window // manager, to make sure we do the relayout before receiving // any other events from the system. //重点关注 requestLayout(); if ((mWindowAttributes.inputFeatures & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) { mInputChannel = new InputChannel(); } try { mOrigWindowType = mWindowAttributes.type; mAttachInfo.mRecomputeGlobalAttributes = true; collectViewAttributes(); // 这里调用了IWindowSession的addToDisplay并且把W类型的mWindow传过去 res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(), mAttachInfo.mContentInsets, mInputChannel); } catch (RemoteException e) { mAdded = false; mView = null; mAttachInfo.mRootView = null; mInputChannel = null; mFallbackEventHandler.setView(null); unscheduleTraversals(); setAccessibilityFocus(null, null); throw new RuntimeException("Adding window failed", e); } finally { if (restore) { attrs.restore(); } } ...... } 现在我们来看看requestLayout函数，这里才是Activity的UI绘制，进去看看发现其实是一个异步任务中执行了那些绘制任务
final class TraversalRunnable implements Runnable { @Override public void run() { doTraversal(); } }void doTraversal() { if (mTraversalScheduled) { mTraversalScheduled = false; mHandler.getLooper().removeSyncBarrier(mTraversalBarrier); if (mProfile) { Debug.startMethodTracing("ViewAncestor"); } Trace.traceBegin(Trace.TRACE_TAG_VIEW, "performTraversals"); try { performTraversals(); } finally { Trace.traceEnd(Trace.TRACE_TAG_VIEW); } if (mProfile) { Debug.stopMethodTracing(); mProfile = false; } } } //这个函数还是比较麻烦的，这里就给出关键点 private void performTraversals() { ...... relayoutResult = relayoutWindow(params, viewVisibility, insetsPending); ...... //一些绘制相关工作 mView.draw(layerCanvas); ...... }private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility, boolean insetsPending) throws RemoteException { float appScale = mAttachInfo.mApplicationScale; boolean restore = false; if (params != null && mTranslator != null) { restore = true; params.backup(); mTranslator.translateWindowLayout(params); } if (params != null) { if (DBG) Log.d(TAG, "WindowLayout in layoutWindow:" + params); } mPendingConfiguration.seq = 0; //Log.d(TAG, ">>>>>> CALLING relayout"); if (params != null && mOrigWindowType != params.type) { // For compatibility with old apps, don't crash here. if (mTargetSdkVersion < android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) { Slog.w(TAG, "Window type can not be changed after " + "the window is added; ignoring change of " + mView); params.type = mOrigWindowType; } } int relayoutResult = mWindowSession.relayout( mWindow, mSeq, params, (int) (mView.getMeasuredWidth() * appScale + 0.5f), (int) (mView.getMeasuredHeight() * appScale + 0.5f), viewVisibility, insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, mWinFrame, mPendingContentInsets, mPendingVisibleInsets, mPendingConfiguration, mSurface); //Log.d(TAG, "<<<<<< BACK FROM relayout"); if (restore) { params.restore(); } if (mTranslator != null) { mTranslator.translateRectInScreenToAppWinFrame(mWinFrame); mTranslator.translateRectInScreenToAppWindow(mPendingContentInsets); mTranslator.translateRectInScreenToAppWindow(mPendingVisibleInsets); } return relayoutResult; }这里是调用了IWindowSession的relayout来获得一个relayoutResult
至此Acitivity的创建和UI的显示就完成了。。。。。。
补充：
既然是Activity的显示，那么必然是少不了显示我们自己设置的UI，一般我们设置的UI都是在OnCreate中的setContentView中设置，现在我们就来看看这个函数到底做了那些事。
Activity中的SetContentView();
public void setContentView(View view) { getWindow().setContentView(view); initActionBar(); }还记得上面所说的Activity显示中有一个Window吧，那个getWindow就是PhoneWindow,那么我们就来看看PhoneWindow中的SetContentView：
@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) { installDecor(); } else { mContentParent.removeAllViews(); } mContentParent.addView(view, params); final Callback cb = getCallback(); if (cb != null && !isDestroyed()) { cb.onContentChanged(); } }这里的mContentParent是一个ViewGroup类型的，这里我们可以看到它把我们设置的view添加进去了，也就是说绘制ViewGroup是也会把它包含的view绘制出来。
接下来再来看看installDector:
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(); mTitleView = (TextView)findViewById(com.android.internal.R.id.title); if (mTitleView != null) { mTitleView.setLayoutDirection(mDecor.getLayoutDirection()); if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) { View titleContainer = findViewById(com.android.internal.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); } } else { mActionBar = (ActionBarView) findViewById(com.android.internal.R.id.action_bar); if (mActionBar != null) { mActionBar.setWindowCallback(getCallback()); if (mActionBar.getTitle() == null) { mActionBar.setWindowTitle(mTitle); } final int localFeatures = getLocalFeatures(); if ((localFeatures & (1 << FEATURE_PROGRESS)) != 0) { mActionBar.initProgress(); } if ((localFeatures & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) { mActionBar.initIndeterminateProgress(); } boolean splitActionBar = false; final boolean splitWhenNarrow = (mUiOptions & ActivityInfo.UIOPTION_SPLIT_ACTION_BAR_WHEN_NARROW) != 0; if (splitWhenNarrow) { splitActionBar = getContext().getResources().getBoolean( com.android.internal.R.bool.split_action_bar_is_narrow); } else { splitActionBar = getWindowStyle().getBoolean( com.android.internal.R.styleable.Window_windowSplitActionBar, false); } final ActionBarContainer splitView = (ActionBarContainer) findViewById( com.android.internal.R.id.split_action_bar); if (splitView != null) { mActionBar.setSplitView(splitView); mActionBar.setSplitActionBar(splitActionBar); mActionBar.setSplitWhenNarrow(splitWhenNarrow); final ActionBarContextView cab = (ActionBarContextView) findViewById( com.android.internal.R.id.action_context_bar); cab.setSplitView(splitView); cab.setSplitActionBar(splitActionBar); cab.setSplitWhenNarrow(splitWhenNarrow); } else if (splitActionBar) { Log.e(TAG, "Requested split action bar with " + "incompatible window decor! Ignoring request."); } // Post the panel invalidate for later; avoid application onCreateOptionsMenu // being called in the middle of onCreate or similar. mDecor.post(new Runnable() { public void run() { // Invalidate if the panel menu hasn't been created before this. PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false); if (!isDestroyed() && (st == null || st.menu == null)) { invalidatePanelMenu(FEATURE_ACTION_BAR); } } }); } } } }从这里我们可以看出这个函数主要是创建了一个DectorView和ViewGroup(mContentPartent)对象以及创建标题栏或者是ActionBar。
再来看看mContentParent：
protected ViewGroup generateLayout(DecorView decor) { ...... mDecor.startChanging(); //layoutResource是一个资源ID View in = mLayoutInflater.inflate(layoutResource, null); decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); //ID_ANDROID_CONTENT是com.android.internal.R.id.content 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); } } ...... return contentPartent; }这里的contentPartent是由findViewById获得，实际是mDectorView的一部分，为什么这么说看看下面的代码就知道了：
public View findViewById(int id) { return getDecorView().findViewById(id); }getDectorView返回的便是mDectorView,到现在我们才算是明白图1-1，其实我们设置的View其实是在DectorView中，而DectorView除了处理我们设置的View还处理了标题栏的显示。。。。。。。。。。。。。。。。。。。
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