事件分发
事件指的是事件流。从手指按下到手指抬起，中间经历数个手指移动
// 事件分发流程，CEO-->总经理-->自己 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup1---->dispatchTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup1---->onInterceptTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup2---->dispatchTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup2---->onInterceptTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: MyView---->dispatchTouchEvent // 自己-->总经理-->CEO 02-22 02:14:52.426 29552-29552/? E/tag: MyView---->onTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup2---->onTouchEvent 02-22 02:14:52.426 29552-29552/? E/tag: ViewGroup1---->onTouchEvent 下面是加上Activity的分发流程 // Activiy分发 02-22 02:17:29.442 29647-29647/? E/tag: MainActivity—->dispatchTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup1—->dispatchTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup1—->onInterceptTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup2—->dispatchTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup2—->onInterceptTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: MyView—->dispatchTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: MyView—->onTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup2—->onTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: ViewGroup1—->onTouchEvent 02-22 02:17:29.442 29647-29647/? E/tag: MainActivity—->onTouchEvent 02-22 02:17:31.394 29647-29647/? E/tag: MainActivity—->dispatchTouchEvent // 无人处理返回给我们的Activity 02-22 02:17:31.394 29647-29647/? E/tag: MainActivity—->onTouchEvent下面根据Activity的dispatchTouchEvent方法，源码
if (getWindow().superDispatchTouchEvent(ev)) { return true; }window的实现是PhoneWindow,那么只需要找到phoneWindow的superDispatchTouchEvent(ev)即可
@Override public boolean superDispatchTouchEvent(MotionEvent event) { // 发现调用的mDecor就是DecorView（FrameLayout） return mDecor.superDispatchTouchEvent(event); }DecorView调用的是下面方法
public boolean superDispatchTouchEvent(MotionEvent event) { // 这里的super指的是谁。DecorView的父类。FrameLayout。其实就是ViewGroup递归，分发事件 return super.dispatchTouchEvent(event); }dispatchTouchEvent的伪代码
@Override public boolean dispatchTouchEvent(MotionEvent ev) { // 如果拦截会调用自己的onTouchEvent(); boolean dissallowIntercept; if(!dissallowIntercept){ dissallowIntercept=onInterceptTouchEvent(ev); } if(dissallowIntercept){ onTouchEvent(ev); }else { // 孩子分发 // 哪个孩子分发呀？根据的是ev.getX()，ev.getY()能够找到哪个孩子在这个范围内 // 如果两个孩子在范围内。 // 根据Z-Order（z轴）传递事件。先让最上面的孩子处理，如果不处理，事件传递到下一个孩子。 // 这里的child应该是个集合 if(child在ev.getX(),ev.getY()之内) child.dispatchTouchEvent(ev); } return super.dispatchTouchEvent(ev); } 一般来说所有的ViewGroup都不拦截ACTION_DOWN。（因为不知道孩子是否处理）一般来说 一旦事件拦截，事件再也不会分发给孩子了。也就是不dispatch给孩子。一般来说，一旦事件拦截之后，再也不会进事件拦截（onInterceptTouchEvent(ev)）方法了（重点）。拦截意味着事件流自己处理。(也就是再也不会问，到底事件交给你处理，还是交给孩子处理)。所以不要再事件拦截方法中根据ev获得一些数据。因为这个方法，一旦决定拦截后，再也不会进入了。系统源码决定。第一种事件冲突的处理方法，在父容器的onInterceptTouchEvent根据条件是否拦截。（ViewPager+DrawLayout）.事件拦截 外部拦截法让孩子决定是否拦截。 getParent().requestDisallowInterceptTouchEvent(）内部拦截法如果一个孩子处理事件ActionDown，那么接下来的事件还会给这个孩子，其他是没有拦截。从WM代码开始
WindowManagerImpl的addView();
@Override public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) { // mGlobal的addView。 // WindowManagerGlobal mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow); }mGlobal的addView
// 顶级节点的布局参数是WindowManager.LayoutParams final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;‘ // 创建 一个ViewRootImpl对象 root = new ViewRootImpl(view.getContext(), display); // 将view添加到ViewRootImpl这里面 root.setView(view, wparams, panelParentView);先分析ViewRootImpl的构造方法
//checkThread()的时候使用 // 将创建ViewRootImpl的线程存起来，以便checkThread() 更新ui的时候做检查 mThread = Thread.currentThread(); // 通过WindowManagerGlobal获得window的session（即wm和wms的通讯回话） mWindowSession = WindowManagerGlobal.getWindowSession(); // session就是会话接下来查看 WindowManagerGlobal.getWindowSession();来知道到底适合谁建立了会话。
public static IWindowSession getWindowSession() { synchronized (WindowManagerGlobal.class) { if (sWindowSession == null) { try { //imm是实现cs通讯的，也就是client和server的通讯（framework和c的通讯）。client指的是ViewRootImpl，Server指的是WMS InputMethodManager imm = InputMethodManager.getInstance(); // 这里获得的是wms IWindowManager windowManager = getWindowManagerService(); // 建立cs连接 //wms和imm简历连接 // 建立viewRootImpl和WMS的连接 sWindowSession = windowManager.openSession( new IWindowSessionCallback.Stub() { @Override public void onAnimatorScaleChanged(float scale) { ValueAnimator.setDurationScale(scale); } }, imm.getClient(), imm.getInputContext()); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } return sWindowSession; }}
接下来查看getWindowManagerService();方法
public static IWindowManager getWindowManagerService() { synchronized (WindowManagerGlobal.class) { if (sWindowManagerService == null) { // 在service錗anager中找到window的binder，通过打开session // AIDL 强转 // ServiceManager专门存储系统级别服务的。可以想象成map sWindowManagerService = IWindowManager.Stub.asInterface( .getService("window")); try { sWindowManagerService = getWindowManagerService(); ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale()); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } return sWindowManagerService; } } ViewRootImpl实现了WMS和view的通讯。接下来分析viewRootImpl的setView（）；里面有一个requestLayout();方法
@Override public void requestLayout() { if (!mHandlingLayoutInLayoutRequest) { // 检查 checkThread(); mLayoutRequested = true; scheduleTraversals(); } }scheduleTraversals
void scheduleTraversals() { if (!mTraversalScheduled) { mTraversalScheduled = true; mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier(); // mTraversalRunnable 是？ mChoreographer.postCallback( Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null); if (!mUnbufferedInputDispatch) { scheduleConsumeBatchedInput(); } notifyRendererOfFramePending(); pokeDrawLockIfNeeded(); } } final class TraversalRunnable implements Runnable { @Override public void run() { // 做 doTraversal(); } }doTraversal
void doTraversal() { if (mTraversalScheduled) { mTraversalScheduled = false; mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier); if (mProfile) { Debug.startMethodTracing("ViewAncestor"); } // 执行perform performTraversals(); if (mProfile) { Debug.stopMethodTracing(); mProfile = false; } } }performTraversals();完成了3件事 // 获得decorView的测量算子 int childWidthMeasureSpec = getRootMeasureSpec(mWidth, lp.width); int childHeightMeasureSpec = getRootMeasureSpec(mHeight, lp.height); // perforMeasure performMeasure(childWidthMeasureSpec, childHeightMeasureSpec); // performLayout performLayout(lp, mWidth, mHeight); // performDraw; performDraw();
performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);
private void performMeasure(int childWidthMeasureSpec, int childHeightMeasureSpec) { Trace.traceBegin(Trace.TRACE_TAG_VIEW, "measure"); try { // 最顶层节点开始递归测量 mView.measure(childWidthMeasureSpec, childHeightMeasureSpec); } finally { Trace.traceEnd(Trace.TRACE_TAG_VIEW); } }performLayout(lp, mWidth, mHeight); 递归layout
performDraw(); mView.draw(canvas);递归绘制。从wm添加view开始。经历wm，wmg，viewRootImp,setView()—>requestLayout–> scheduleTraversals–doTraversal–>performTravaersal–>performMeasure–>performLayout–startActivity开始
@Override public void startActivityForResult( String who, Intent intent, int requestCode, @Nullable Bundle options) { Uri referrer = onProvideReferrer(); if (referrer != null) { intent.putExtra(Intent.EXTRA_REFERRER, referrer); } // mInstrumentation启动的Activity Instrumentation.ActivityResult ar = mInstrumentation.execStartActivity( this, mMainThread.getApplicationThread(), mToken, who, intent, requestCode, options); if (ar != null) { mMainThread.sendActivityResult( mToken, who, requestCode, ar.getResultCode(), ar.getResultData()); } cancelInputsAndStartExitTransition(options); } mInstrumentation.execStartActivity //AMS.startActivity int result = ActivityManagerNative.getDefault() .startActivity(whoThread, who.getBasePackageName(), intent, intent.resolveTypeIfNeeded(who.getContentResolver()), token, target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);AMS的startActivity（）调用了startActivityAsUser()
@Override public final int startActivityAsUser(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId) { enforceNotIsolatedCaller("startActivity"); userId = mUserController.handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId, false, ALLOW_FULL_ONLY, "startActivity", null); // TODO: Switch to user app stacks here. return mActivityStarter.startActivityMayWait(caller, -1, callingPackage, intent, resolvedType, null, null, resultTo, resultWho, requestCode, startFlags, profilerInfo, null, null, bOptions, false, userId, null, null); } startActivityMayWait // mSupervisor解析intent。其实是通讯PMS来解析的。PMS在开机时候会扫描所有的app的清单文件，找到activity存起来。 ResolveInfo rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId) startActivityLocked（）；最终调用ActivityStackSupervisor的realStartActivityLocked
// thread指的是APPLICATIONTHRE app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken, System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration), new Configuration(task.mOverrideConfig), r.compat, r.launchedFromPackage, task.voiceInteractor, app.repProcState, r.icicle, r.persistentState, results, newIntents, !andResume, mService.isNextTransitionForward(), profilerInfo);ApplicationThread.scheduleLaunchActivity
sendMessage(H.LAUNCH_ACTIVITY, r);调用 handleLaunchActivity(r, null, “LAUNCH_ACTIVITY”);
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) { Activity a = performLaunchActivity(r, customIntent); if (a != null) { handleResumeActivity(r.token, false, r.isForward, !r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason); } else { } }performLaunchActivity 完成了三件事。创建一个Activity，以及回调onCreat，onStart
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) { Activity activity = null; try { java.lang.ClassLoader cl = r.packageInfo.getClassLoader(); // 创建一个Activity对象 activity = mInstrumentation.newActivity( cl, component.getClassName(), r.intent); } catch (Exception e) { } try { if (activity != null) { // 各种context服务。都放在createBaseContextForActivity注册的。 // getSystemService, Context appContext = createBaseContextForActivity(r, activity); Window window = null; if (r.mPendingRemoveWindow != null && r.mPreserveWindow) { window = r.mPendingRemoveWindow; r.mPendingRemoveWindow = null; r.mPendingRemoveWindowManager = null; } // 绑定下 activity.attach(appContext, this, getInstrumentation(), r.token, r.ident, app, r.intent, r.activityInfo, title, r.parent, r.embeddedID, r.lastNonConfigurationInstances, config, r.referrer, r.voiceInteractor, window); if (r.isPersistable()) { // 回调activity的onCreate方法 mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState); } else { mInstrumentation.callActivityOnCreate(activity, r.state); } if (!r.activity.mFinished) { if (r.isPersistable()) { // 调用onRestore方法 if (r.state != null || r.persistentState != null) { mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state, r.persistentState); } } else if (r.state != null) { mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state); } } if (!r.activity.mFinished) { // 调用Activity的onStart方法 activity.performStart(); r.stopped = false; } r.paused = true; mActivities.put(r.token, r); } catch (SuperNotCalledException e) { throw e; } catch (Exception e) { if (!mInstrumentation.onException(activity, e)) { throw new RuntimeException( "Unable to start activity " + component + ": " + e.toString(), e); } } return activity;}
handleResumeActivity
final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) { // 执行resume方法 r = performResumeActivity(token, clearHide, reason);
if (r != null) { final Activity a = r.activity; 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) { a.mWindowAdded = true; // WM和decor关联起来了。执行了第二部分代码。完成view的测量布局绘制，显示、 wm.addView(decor, l); } } Activity的启动流程，Insturmentation调用ASM启动Activity。ASM在启动Activity的时候让PMS解析以下要启动的Activity。之后交给ActivityStatckSuperior.realSatrtActivity。再交给ApplicatoinThread.scheaclLuanchActvity()。handleLaunchActivity方法完成Activity的创建以及onCreate，onstart方法的调用（performLuanchActivity）.之后完成Activity的onResume。最后将window的decorView添加到WM上，有ViewRootImpl完成测量布局绘制显示给用户。* installDecor();
private void installDecor() { mForceDecorInstall = false; if (mDecor == null) { // 产生decorView Window的最顶层节点 mDecor = generateDecor(-1); mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); } else { // 将decorView和window关联起来 mDecor.setWindow(this); } if (mContentParent == null) { // 根据decorview产生我们的ContentParent也就是id为content的viewGroup, // 根据不同的requestFeature找到不同的布局文件 // 天假给decorView.之后将id为content的view找到 // 添加给mContentParent mContentParent = generateLayout(mDecor); } }* phoneWindow的主要功能就是装饰。给布局文件添加不同decor层次。根据不同的reuqestfreature添加不同的layoutresource。直接给view交互，通过viewrootimpl。
我们经常调用
context.getSystemService(Context.LAYOUT_INFLATE_SERVICE)获得LayoutInflater对象。那么这个对象是什么时候注册到Context中的呢?这个对象的具体实现类是谁？
LayoutInflater这个服务，是在创建Activity的时候，作为baseContext传递给Activity的。接下来我们看源码过程。我们知道Activity的创建过程是在ApplicationThread的performLaunchActivity方法中。那么接下来我们分析这个方法
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) { /*/ Activity activity = null; try{ // 通过Instrumentation类创建Activity java.lang.ClassLoader cl = r.packageInfo.getClassLoader(); activity = mInstrumentation.newActivity( cl, component.getClassName(), r.intent); }catch(Exeception e){} /*/ // 创建Context过程，也就是baseContext Context appContext = createBaseContextForActivity(r, activity); // 关联activity和baseContext activity.attach(appContext, this, getInstrumentation(), r.token, r.ident, app, r.intent, r.activityInfo, title, r.parent, r.embeddedID, r.lastNonConfigurationInstances, config, r.referrer, r.voiceInteractor, window); }那么接下来我们只要分析
Context appContext = createBaseContextForActivity(r, activity);这个方法即可，源码继续
private Context createBaseContextForActivity(ActivityClientRecord r, final Activity activity) { // 通过调用ContextImpl的静态方法创建baseContext对象 ContextImpl appContext = ContextImpl.createActivityContext( this, r.packageInfo, r.token, displayId, r.overrideConfig); appContext.setOuterContext(activity); return baseContext; }接下来分析
ContextImpl.createActivityContext( this, r.packageInfo, r.token, displayId, r.overrideConfig); appContext.setOuterContext(activity);接下来我们分析下ContextImpl这个类，发现其有一个成员变量
// 在这里注册系统级别的服务 // The system service cache for the system services that are cached per-ContextImpl. final Object[] mServiceCache = SystemServiceRegistry.createServiceCache();SystemServiceRegistry类有个静态代码块，完成了常用服务的注册，代码如下
static{ // 注册LayoutLAYOUT_INFLATER_SERVICE系统服务，具体实现类是PhoneLayoutInflater registerService(Context.LAYOUT_INFLATER_SERVICE, LayoutInflater.class, new CachedServiceFetcher<LayoutInflater>() { @Override public LayoutInflater createService(ContextImpl ctx) { return new PhoneLayoutInflater(ctx.getOuterContext()); }}); // 注册AM registerService(Context.ACTIVITY_SERVICE, ActivityManager.class, new CachedServiceFetcher<ActivityManager>() { @Override public ActivityManager createService(ContextImpl ctx) { return new ActivityManager(ctx.getOuterContext(), ctx.mMainThread.getHandler()); }}); // 注册WM registerService(Context.WINDOW_SERVICE, WindowManager.class, new CachedServiceFetcher<WindowManager>() { @Override public WindowManager createService(ContextImpl ctx) { return new WindowManagerImpl(ctx); }}); // 等等 }接下来我们看inflate过程，下面是整个inflate过程
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) { synchronized (mConstructorArgs) { Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate"); final Context inflaterContext = mContext; final AttributeSet attrs = Xml.asAttributeSet(parser); Context lastContext = (Context) mConstructorArgs[0]; mConstructorArgs[0] = inflaterContext; View result = root; try { // 循环找到第一个view节点， int type; while ((type = parser.next()) != XmlPullParser.START_TAG && type != XmlPullParser.END_DOCUMENT) { // Empty } // 这里判断是否是第一个view节点 if (type != XmlPullParser.START_TAG) { throw new InflateException(parser.getPositionDescription() + ": No start tag found!"); } final String name = parser.getName(); // 解析merge标签 if (TAG_MERGE.equals(name)) { if (root == null || !attachToRoot) { throw new InflateException("<merge /> can be used only with a valid " + "ViewGroup root and attachToRoot=true"); } // 通过rInflate方法将merge标签下的孩子直接合并到root上，这样减少一层布局，达到减少viewTree的目的 rInflate(parser, root, inflaterContext, attrs, false); } else { // 调用反射创建view对象 final View temp = createViewFromTag(root, name, inflaterContext, attrs); ViewGroup.LayoutParams params = null; if (root != null) { // Create layout params that match root, if supplied params = root.generateLayoutParams(attrs); if (!attachToRoot) { // 如果view的父容器不为null，并且attachToRoot未true得话，这里只是让刚刚通过反射创建的view使用root（父容器的布局参数） temp.setLayoutParams(params); } } // 通过深度遍历temp下的节点，之后将节点依次添加到刚刚通过反射创建的temp对象上，因为采用的是深度优先遍历算法，因此viewTree的层级很深的话，会影响遍历的性能 rInflateChildren(parser, temp, attrs, true); // 判断刚刚创建的temp对象是否添加到父节点上. // 满足两个条件1 父节点(root)不为null，2 attachToRoot=true if (root != null && attachToRoot) { root.addView(temp, params); } // 设置result if (root == null || !attachToRoot) { result = temp; } } } catch (XmlPullParserException e) { final InflateException ie = new InflateException(e.getMessage(), e); ie.setStackTrace(EMPTY_STACK_TRACE); throw ie; } catch (Exception e) { } finally { // Don't retain static reference on context. mConstructorArgs[0] = lastContext; mConstructorArgs[1] = null; Trace.traceEnd(Trace.TRACE_TAG_VIEW); } // 返回 return result; }}
通过上面分析，我们对inflate的整体过程有了一个了解，也见到了merge标签（经常作为布局文件根节点，来达到减少viewTree的层次）接下来，我们分析4个方法rInflate(parser, root, inflaterContext, attrs, false);，其实不管是根节点为merge还是普通的view（最终都会用这个方法），深度遍历添加view下面是代码
// 深度遍历添加孩子 void rInflate(XmlPullParser parser, View parent, Context context, AttributeSet attrs, boolean finishInflate) throws XmlPullParserException, IOException { final int depth = parser.getDepth(); int type; while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) { if (type != XmlPullParser.START_TAG) { continue; } final String name = parser.getName(); if (TAG_REQUEST_FOCUS.equals(name)) { parseRequestFocus(parser, parent); } else if (TAG_TAG.equals(name)) { // 如果我们调用了View.setTag()，将会执行下面代码 parseViewTag(parser, parent, attrs); // include不能作为根节点 } else if (TAG_INCLUDE.equals(name)) { if (parser.getDepth() == 0) { throw new InflateException("<include /> cannot be the root element"); } // 这里解析include标签代码 parseInclude(parser, context, parent, attrs); } else if (TAG_MERGE.equals(name)) { // merge一定是根节点 throw new InflateException("<merge /> must be the root element"); } else { final View view = createViewFromTag(parent, name, context, attrs); final ViewGroup viewGroup = (ViewGroup) parent; final ViewGroup.LayoutParams params = viewGroup.generateLayoutParams(attrs); // 递归，因为rInflateChildren最终还会调用rInflate(parser, parent, parent.getContext(), attrs, finishInflate);方法 rInflateChildren(parser, view, attrs, true); viewGroup.addView(view, params); } } if (finishInflate) { // viewTree填充完毕，回调自定义view经常使用的onFinishInflate方法 parent.onFinishInflate(); } }rInflateChildren(parser, view, attrs, true);方法
// 直接调用rInflate()实现ViewTree final void rInflateChildren(XmlPullParser parser, View parent, AttributeSet attrs, boolean finishInflate) throws XmlPullParserException, IOException { rInflate(parser, parent, parent.getContext(), attrs, finishInflate);}
createViewFromTag(root, name, inflaterContext, attrs);方法，这个方法其实处理了自定义view和系统view的创建。最终调用了下面方法
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs, boolean ignoreThemeAttr) { if (name.equals("view")) { name = attrs.getAttributeValue(null, "class"); } // 设置view默认样式 if (!ignoreThemeAttr) { final TypedArray ta = context.obtainStyledAttributes(attrs, ATTRS_THEME); final int themeResId = ta.getResourceId(0, 0); if (themeResId != 0) { context = new ContextThemeWrapper(context, themeResId); } ta.recycle(); } try { View view; if (view == null) { final Object lastContext = mConstructorArgs[0]; mConstructorArgs[0] = context; try {//创建系统view的方法，因为系统view的标签不是完整类名，需要会在 onCreateView中完成拼接（拼接出系统view的完整类名） if (-1 == name.indexOf('.')) { view = onCreateView(parent, name, attrs); } else { //自定义view的创建 view = createView(name, null, attrs); } } finally { mConstructorArgs[0] = lastContext; } } return view; } catch (InflateException e) { throw e; } catch (ClassNotFoundException e) { final InflateException ie = new InflateException(attrs.getPositionDescription() + ": Error inflating class " + name, e); ie.setStackTrace(EMPTY_STACK_TRACE); throw ie; } catch (Exception e) { final InflateException ie = new InflateException(attrs.getPositionDescription() + ": Error inflating class " + name, e); ie.setStackTrace(EMPTY_STACK_TRACE); throw ie; } }接下来我们分析 createView(String name, String prefix, AttributeSet attrs)方法，系统view的创建，最终也会调用createView方法。只不过在前面拼接上了系统view的包名。
public final View createView(String name, String prefix, AttributeSet attrs) throws ClassNotFoundException, InflateException { // 获取view的构造方法 Constructor<? extends View> constructor = sConstructorMap.get(name); // 验证 if (constructor != null && !verifyClassLoader(constructor)) { constructor = null; sConstructorMap.remove(name); } Class<? extends View> clazz = null; try { if (constructor == null) { clazz = mContext.getClassLoader().loadClass( prefix != null ? (prefix + name) : name).asSubclass(View.class); if (mFilter != null && clazz != null) { boolean allowed = mFilter.onLoadClass(clazz); if (!allowed) { failNotAllowed(name, prefix, attrs); } } constructor = clazz.getConstructor(mConstructorSignature); constructor.setAccessible(true); // 将view的构造方法缓存起来 sConstructorMap.put(name, constructor); } else { /*/ } Object[] args = mConstructorArgs; args[1] = attrs; // 反射创建view对象 final View view = constructor.newInstance(args); // 对viewStub进行处理 if (view instanceof ViewStub) { // 给ViewStub设置LayoutInfalter.什么时候inflate，什么时候viewStub的内容才显示，（比GONE性能好） final ViewStub viewStub = (ViewStub) view; viewStub.setLayoutInflater(cloneInContext((Context) args[0])); } return view; } catch (NoSuchMethodException e) { } catch (ClassCastException e) { } catch (ClassNotFoundException e) { } catch (Exception e) { } finally { } }