popwindow和dialog相信大家在开发过程中已经用的很多了，但是很多人对其中的机制以及两者间的区别不甚了解，在谈论之前，先说几个问题
1.popwindow和dialog都能在activity的oncreate中show么？
2.popwindow和dialog都是子窗口类型么？
3.dialog和popwindow的共同点和区别点？
要明确的回答这三个问题，必须要在这两个类的源码中找答案了
这篇文章先来说下dialog
dialog的初始化代码如下
Dialog dialog = new Dialog(this);
dialog.setContentView(R.layout.dialog_test);
dialog.show();
可以看到这里new了一个dialog参数必须是所依附的activity的context,
那application的context可以么？去看下它的构造参数把
//关键点1
if (createContextThemeWrapper) {
if (themeResId == ResourceId.ID_NULL) {
final TypedValue outValue = new TypedValue();
context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true);
themeResId = outValue.resourceId;
}
mContext = new ContextThemeWrapper(context, themeResId);
} else {
mContext = context;
}
//关键点2
mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
//关键点3
final Window w = new PhoneWindow(mContext);
mWindow = w;
//关键点4
w.setCallback(this)；
w.setOnWindowDismissedCallback(this);
w.setOnWindowSwipeDismissedCallback(() -> {
if (mCancelable) {
cancel();
}
});
//关键点5
w.setWindowManager(mWindowManager, null, null);
w.setGravity(Gravity.CENTER);
mListenersHandler = new ListenersHandler(this);
这里有几个点很明确：
1.dialog可以用自带的主题，如果外面设置进来就用外面的主题
2.就是获取了mWindowManager的对象，大家都知道，mWindowManager相当于管家，添加，移除，和更改window都是通过
mWindowManager来操作的，显然看WindowManager的源码得知里面包含了window一系列的信息
/**
* Identifier for this window. This will usually be filled in for
* you.
*/
public IBinder token = null;
/**
* Name of the package owning this window.
*/
public String packageName = null;
public static final int TYPE_APPLICATION_STARTING = 3;
/**
* Window type: a variation on TYPE_APPLICATION that ensures the window
* manager will wait for this window to be drawn before the app is shown.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_DRAWN_APPLICATION = 4;
/**
* End of types of application windows.
*/
public static final int LAST_APPLICATION_WINDOW = 99;
/**
* Start of types of sub-windows. The {@link #token} of these windows
* must be set to the window they are attached to. These types of
* windows are kept next to their attached window in Z-order, and their
* coordinate space is relative to their attached window.
*/
public static final int FIRST_SUB_WINDOW = 1000;
包括了此window的token，类型，所在的包名，还有一些属性参数等都包括在了里面
那如果用了context的所属activity的话，这些参数包含的都是activity里面创建出来window的信息了
3.创建了phonewindow以前我一直误认为创建了phonewindow就是有个新的window，没有创建就没有window，其实不然，phonewindow里只是对DecorView的创建，以及对一些window的属性初始化罢了
比如这个window是否是悬浮的，大小，动画等
4.这里设置了一个window的回调用，是关于事件的分发的，过会再说
5.这里用window绑定了windowmanager
这个方法注意是为此window绑定了一个它的windowmanager（其实没啥用，后面会说）
在初始化之后，把布局放进了window的contentview以后就调用了show方法
public void show() {
if (mShowing) {
if (mDecor != null) {
if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);
}
mDecor.setVisibility(View.VISIBLE);
}
return;
}
mCanceled = false;
if (!mCreated) {
dispatchOnCreate(null);
} else {
// Fill the DecorView in on any configuration changes that
// may have occured while it was removed from the WindowManager.
final Configuration config = mContext.getResources().getConfiguration();
mWindow.getDecorView().dispatchConfigurationChanged(config);
}
onStart();
mDecor = mWindow.getDecorView();
if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
final ApplicationInfo info = mContext.getApplicationInfo();
mWindow.setDefaultIcon(info.icon);
mWindow.setDefaultLogo(info.logo);
mActionBar = new WindowDecorActionBar(this);
}
WindowManager.LayoutParams l = mWindow.getAttributes();
boolean restoreSoftInputMode = false;
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {
l.softInputMode |=
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
restoreSoftInputMode = true;
}
//关键点1
mWindowManager.addView(mDecor, l);
if (restoreSoftInputMode) {
l.softInputMode &=
~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
}
mShowing = true;
sendShowMessage();
}
这里关键点1便是windowmanager.addview的方法了，此方法会调用windowmanagerImp的addview方法
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}
这里的mParentWindow其实就是依附的activity的window，和自身的window其实没有关系，紧接着调用了WindowManagerGlobal的addview方法
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) {
//关键点1
parentWindow.adjustLayoutParamsForSubWindow(wparams);
} else {
// If there's no parent, then hardware acceleration for this view is
// set from the application's hardware acceleration setting.
final Context context = view.getContext();
if (context != null
&& (context.getApplicationInfo().flags
& ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
}
}
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 (int i = mRoots.size() - 1; i >= 0; --i) {
mRoots.get(i).loadSystemProperties();
}
}
}
};
SystemProperties.addChangeCallback(mSystemPropertyUpdater);
}
int index = findViewLocked(view, false);
if (index >= 0) {
if (mDyingViews.contains(view)) {
// Don't wait for MSG_DIE to make it's way through root's queue.
mRoots.get(index).doDie();
} else {
throw new IllegalStateException("View " + view
+ " has already been added to the window manager.");
}
// The previous removeView() had not completed executing. Now it has.
}
// If this is a panel window, then find the window it is being
// attached to for future reference.
//关键点2
if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
final int count = mViews.size();
for (int i = 0; i < count; i++) {
if (mRoots.get(i).mWindow.asBinder() == wparams.token) {
panelParentView = mViews.get(i);
}
}
}
//关键点3
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
// do this last because it fires off messages to start doing things
try {
//关键点4
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
}
}
这里有四个关键点
1.会调用parentWindow .adjustLayoutParamsForSubWindow这个方法
void adjustLayoutParamsForSubWindow(WindowManager.LayoutParams wp) {
CharSequence curTitle = wp.getTitle();
if (wp.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
wp.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
if (wp.token == null) {
View decor = peekDecorView();
if (decor != null) {
wp.token = decor.getWindowToken();
}
}
if (curTitle == null || curTitle.length() == 0) {
final StringBuilder title = new StringBuilder(32);
if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_MEDIA) {
title.append("Media");
} else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_MEDIA_OVERLAY) {
title.append("MediaOvr");
} else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_PANEL) {
title.append("Panel");
} else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_SUB_PANEL) {
title.append("SubPanel");
} else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_ABOVE_SUB_PANEL) {
title.append("AboveSubPanel");
} else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG) {
title.append("AtchDlg");
} else {
title.append(wp.type);
}
if (mAppName != null) {
title.append(":").append(mAppName);
}
wp.setTitle(title);
}
} else if (wp.type >= WindowManager.LayoutParams.FIRST_SYSTEM_WINDOW &&
wp.type <= WindowManager.LayoutParams.LAST_SYSTEM_WINDOW) {
// We don't set the app token to this system window because the life cycles should be
// independent. If an app creates a system window and then the app goes to the stopped
// state, the system window should not be affected (can still show and receive input
// events).
if (curTitle == null || curTitle.length() == 0) {
final StringBuilder title = new StringBuilder(32);
title.append("Sys").append(wp.type);
if (mAppName != null) {
title.append(":").append(mAppName);
}
wp.setTitle(title);
}
} else {
if (wp.token == null) {
//关键点1.1
wp.token = mContainer == null ? mAppToken : mContainer.mAppToken;
}
if ((curTitle == null || curTitle.length() == 0)
&& mAppName != null) {
wp.setTitle(mAppName);
}
}
if (wp.packageName == null) {
wp.packageName = mContext.getPackageName();
}
if (mHardwareAccelerated ||
(mWindowAttributes.flags & FLAG_HARDWARE_ACCELERATED) != 0) {
wp.flags |= FLAG_HARDWARE_ACCELERATED;
}
}
关键点1.1
这方法就给这个window设置token的，我们可以看到由于在dialog中用了phonewindow所以，window的类型就是应用窗口了，也就走到了else里了所以是在这里设置的token的，popwindow后文会说
关键点2
也就是非应用窗口赋值panelParentView的地方，与dialog其实关系不大
关键点3
这里新建了ViewRootImpl对象，可以这么说，每一个window都有一个
ViewRootImpl对象，里面封装着很多东西
public ViewRootImpl(Context context, Display display) {
mContext = context;
mWindowSession = WindowManagerGlobal.getWindowSession();
mDisplay = display;
mBasePackageName = context.getBasePackageName();
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);
mTargetSdkVersion = context.getApplicationInfo().targetSdkVersion;
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(mWindowSession, mWindow, display, this, mHandler, this,
context);
mAccessibilityManager = AccessibilityManager.getInstance(context);
mAccessibilityManager.addAccessibilityStateChangeListener(
mAccessibilityInteractionConnectionManager, mHandler);
mHighContrastTextManager = new HighContrastTextManager();
mAccessibilityManager.addHighTextContrastStateChangeListener(
mHighContrastTextManager, mHandler);
mViewConfiguration = ViewConfiguration.get(context);
mDensity = context.getResources().getDisplayMetrics().densityDpi;
mNoncompatDensity = context.getResources().getDisplayMetrics().noncompatDensityDpi;
mFallbackEventHandler = new PhoneFallbackEventHandler(context);
mChoreographer = Choreographer.getInstance();
mDisplayManager = (DisplayManager)context.getSystemService(Context.DISPLAY_SERVICE);
if (!sCompatibilityDone) {
sAlwaysAssignFocus = mTargetSdkVersion < Build.VERSION_CODES.P;
sCompatibilityDone = true;
}
loadSystemProperties();
}
可以看到，里面初始化了windowSession，这个进行IPC的时候会用到，还有mAttachInfo对象，是view和viewImp的桥梁包括还有mChoreographer对象是屏幕刷新的对象，顺便说一句，view.post时，执行的时机，就是有了这个mAttachInfo才放到消息队列等待执行的
在看下关键点四
也是最重要的方法，走到了viewRootImp的setView方法
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
mAttachInfo.mDisplayState = mDisplay.getState();
mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
mViewLayoutDirectionInitial = mView.getRawLayoutDirection();
mFallbackEventHandler.setView(view);
mWindowAttributes.copyFrom(attrs);
if (mWindowAttributes.packageName == null) {
mWindowAttributes.packageName = mBasePackageName;
}
attrs = mWindowAttributes;
setTag();
if (DEBUG_KEEP_SCREEN_ON && (mClientWindowLayoutFlags
& WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) != 0
&& (attrs.flags&WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) == 0) {
Slog.d(mTag, "setView: FLAG_KEEP_SCREEN_ON changed from true to false!");
}
// Keep track of the actual window flags supplied by the client.
mClientWindowLayoutFlags = attrs.flags;
setAccessibilityFocus(null, null);
if (view instanceof RootViewSurfaceTaker) {
mSurfaceHolderCallback =
((RootViewSurfaceTaker)view).willYouTakeTheSurface();
if (mSurfaceHolderCallback != null) {
mSurfaceHolder = new TakenSurfaceHolder();
mSurfaceHolder.setFormat(PixelFormat.UNKNOWN);
mSurfaceHolder.addCallback(mSurfaceHolderCallback);
}
}
// Compute surface insets required to draw at specified Z value.
// TODO: Use real shadow insets for a constant max Z.
if (!attrs.hasManualSurfaceInsets) {
attrs.setSurfaceInsets(view, false /*manual*/, true /*preservePrevious*/);
}
CompatibilityInfo compatibilityInfo =
mDisplay.getDisplayAdjustments().getCompatibilityInfo();
mTranslator = compatibilityInfo.getTranslator();
// If the application owns the surface, don't enable hardware acceleration
if (mSurfaceHolder == null) {
// While this is supposed to enable only, it can effectively disable
// the acceleration too.
enableHardwareAcceleration(attrs);
final boolean useMTRenderer = MT_RENDERER_AVAILABLE
&& mAttachInfo.mThreadedRenderer != null;
if (mUseMTRenderer != useMTRenderer) {
// Shouldn't be resizing, as it's done only in window setup,
// but end just in case.
endDragResizing();
mUseMTRenderer = useMTRenderer;
}
}
boolean restore = false;
if (mTranslator != null) {
mSurface.setCompatibilityTranslator(mTranslator);
restore = true;
attrs.backup();
mTranslator.translateWindowLayout(attrs);
}
if (DEBUG_LAYOUT) Log.d(mTag, "WindowLayout in setView:" + attrs);
if (!compatibilityInfo.supportsScreen()) {
attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
mLastInCompatMode = true;
}
mSoftInputMode = attrs.softInputMode;
mWindowAttributesChanged = true;
mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;
mAttachInfo.mRootView = view;
mAttachInfo.mScalingRequired = mTranslator != null;
mAttachInfo.mApplicationScale =
mTranslator == null ? 1.0f : mTranslator.applicationScale;
if (panelParentView != null) {
mAttachInfo.mPanelParentWindowToken
= panelParentView.getApplicationWindowToken();
}
mAdded = true;
int res; /* = WindowManagerImpl.ADD_OKAY; */
// 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.
//关键点一
requestLayout();
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
mInputChannel = new InputChannel();
}
mForceDecorViewVisibility = (mWindowAttributes.privateFlags
& PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY) != 0;
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
//关键点二
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(), mWinFrame,
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, 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();
}
}
if (mTranslator != null) {
mTranslator.translateRectInScreenToAppWindow(mAttachInfo.mContentInsets);
}
mPendingOverscanInsets.set(0, 0, 0, 0);
mPendingContentInsets.set(mAttachInfo.mContentInsets);
mPendingStableInsets.set(mAttachInfo.mStableInsets);
mPendingDisplayCutout.set(mAttachInfo.mDisplayCutout);
mPendingVisibleInsets.set(0, 0, 0, 0);
mAttachInfo.mAlwaysConsumeNavBar =
(res & WindowManagerGlobal.ADD_FLAG_ALWAYS_CONSUME_NAV_BAR) != 0;
mPendingAlwaysConsumeNavBar = mAttachInfo.mAlwaysConsumeNavBar;
if (DEBUG_LAYOUT) Log.v(mTag, "Added window " + mWindow);
if (res < WindowManagerGlobal.ADD_OKAY) {
mAttachInfo.mRootView = null;
mAdded = false;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
switch (res) {
case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not valid; is your activity running?");
case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not for an application");
case WindowManagerGlobal.ADD_APP_EXITING:
throw new WindowManager.BadTokenException(
"Unable to add window -- app for token " + attrs.token
+ " is exiting");
case WindowManagerGlobal.ADD_DUPLICATE_ADD:
throw new WindowManager.BadTokenException(
"Unable to add window -- window " + mWindow
+ " has already been added");
case WindowManagerGlobal.ADD_STARTING_NOT_NEEDED:
// Silently ignore -- we would have just removed it
// right away, anyway.
return;
case WindowManagerGlobal.ADD_MULTIPLE_SINGLETON:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- another window of type "
+ mWindowAttributes.type + " already exists");
case WindowManagerGlobal.ADD_PERMISSION_DENIED:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- permission denied for window type "
+ mWindowAttributes.type);
case WindowManagerGlobal.ADD_INVALID_DISPLAY:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified display can not be found");
case WindowManagerGlobal.ADD_INVALID_TYPE:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified window type "
+ mWindowAttributes.type + " is not valid");
}
throw new RuntimeException(
"Unable to add window -- unknown error code " + res);
}
if (view instanceof RootViewSurfaceTaker) {
mInputQueueCallback =
((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();
}
//关键点三
if (mInputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
}
//关键点四
view.assignParent(this);
mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
if (mAccessibilityManager.isEnabled()) {
mAccessibilityInteractionConnectionManager.ensureConnection();
}
if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
// Set up the input pipeline.
CharSequence counterSuffix = attrs.getTitle();
mSyntheticInputStage = new SyntheticInputStage();
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
mFirstInputStage = nativePreImeStage;
mFirstPostImeInputStage = earlyPostImeStage;
mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
}
}
}
代码比较长，分开来说
关键点一是进行一次request也就是scheduleTraversals方法，进行第一次的测量，布局和绘制这里是一个消息队列的方法所以是要等到每16ms屏幕刷新给上层回掉的时候才会调用。
关键点二便是对window进行一些初始化的操作了，大家有没有想过，为啥dialog这个window会浮在activity这个window上面的，还有popwindow为啥是浮在dialog和activity之上的，为啥新打开一个activity的window会覆盖原来的activity的window
这其实都和window的layer有关，而mWindowSession.addToDisplay就是来判断这些window层级显示顺序，由于这个是WMS的方法，其实调用的就是session的addToDisplay方法，间接调用了windowmanagerservice的addwindow方法,
public int addWindow(Session session, IWindow client, int seq,
LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame,
Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {
int[] appOp = new int[1];
int res = mPolicy.checkAddPermission(attrs, appOp);
if (res != WindowManagerGlobal.ADD_OKAY) {
return res;
......
}
这里的session是system_server进程和app进程的桥梁
这方法具体做的事情就是验证window的有效性和新建了windowState对象，其实window具体的表现形式就是windowState,有多少windowState就是多少window(这里说的window包括了子window)
举个例子：activity中创建的window是windowState,而dialog也是一个windowState,都是应用类型window，只不过依附的token是activity的token，插入的顺序依据的所附属的activity决定的，而popwindow也是一个windowState，只不过它是属于子window的类型，是根据mSubLayer的插入的，这个值越大，越靠前，可以看下LooperJing对于window的分析了，可以说是解析window最详细的文章了，不过是基于6.0的，现在8.0中wms代码稍有变化，本质是一样的
在来看下关键点三，这里创建了一个mInputChannel，当然底层也是相当的复杂，以后专门抽一篇文章来说，主要作用是注册一个native事件，然后当用户触摸到屏幕了，这个native事件会给java层回调，从而进行事件的分发，其实在这里面也进行了跨进程的交互，只不过用的是socket的方法
关键点四就比较简单了，为view设置了一个虚拟的viewparent也就是viewRootImp
总的来说dialog的显示也就说完了，来总结一下：
1.本质和activity的window一样，只不过它的一些属性是特定的，所以在window显示中会不一样。
2,关于dialog的事件，由于是在activity的window之上，并且注册了事件，所以在显示的外部事件是先传给dialog的，当然有属性可以改变这个默认的规则。
3 dialog和activity公用一个windowManager,也就是同一个token，所以在oncreate时因为windowManger已经创建了，所以dialog的token也是不为null的，可以在oncreate中show()
4.所有dialog的动画其实就是winodow的动画，dialog也可以按照style设置不同的主题
ps:dialog和popwindow不同于activity，activity在执行onResume后触发windowManager的add的操作，而这两个却不同
下篇文章分析popwindow的显示，并且说下两者间的区别