最近在改bug的時(shí)候發(fā)現(xiàn)在windowManager.addView的時(shí)候會(huì)發(fā)生莫名其妙的崩潰，那個(gè)崩潰真的是讓你心態(tài)爆炸，潛心研究了兩天window相關(guān)的東西，雖然不是很深?yuàn)W的東西，本人也只是弄清楚了window的添加邏輯，在此分享給大家：
一、懸浮窗的概念
在android中，無(wú)論我們的app界面，還是系統(tǒng)桌面，再或者是手機(jī)下方的幾個(gè)虛擬按鍵和最上方的狀態(tài)欄，又或者是一個(gè)吐司。。。我們所看到的所有界面，都是由一個(gè)個(gè)懸浮窗口組成的。
但是這些窗口有不同的級(jí)別：
基于上述三種，android把懸浮窗劃分成三個(gè)級(jí)別，并通過(guò)靜態(tài)int型變量來(lái)表示：
/** * Start of system-specific window types. These are not normally * created by applications. **/ public static final int FIRST_SYSTEM_WINDOW = 2000; /** * End of types of system windows. **/ public static final int LAST_SYSTEM_WINDOW = 2999;
2000~2999：在系統(tǒng)級(jí)別的懸浮窗范圍內(nèi)，一般我們要想創(chuàng)建是需要申請(qǐng)權(quán)限。
public static final int FIRST_SUB_WINDOW = 1000; /** * End of types of sub-windows. **/ public static final int LAST_SUB_WINDOW = 1999;
1000~1999：子窗口級(jí)別的懸浮窗，他如果想要?jiǎng)?chuàng)建必須在一個(gè)父窗口下。
public static final int TYPE_BASE_APPLICATION = 1;public static final int LAST_APPLICATION_WINDOW = 99;
1~99：應(yīng)用程序級(jí)別的懸浮窗，作為每個(gè)應(yīng)用程序的基窗口。
在每段的范圍內(nèi)都有眾多個(gè)窗口類型，這個(gè)具體就不說(shuō)了，因?yàn)樘嗔烁菊f(shuō)不完。。
但是說(shuō)了這么半天，懸浮窗到底是個(gè)啥東西，可能這個(gè)名詞聽(tīng)得很多，但是仔細(xì)想想android中用到的哪個(gè)控件還是哪個(gè)類叫懸浮窗？沒(méi)有吧，那么View總該知道吧（不知道別說(shuō)你是做android的）
其實(shí)說(shuō)白了懸浮窗就是一個(gè)被包裹的view。因?yàn)槌艘粋€(gè)view他還有很多的屬性：長(zhǎng)寬深度，類型，證書等等東西，只是屬性很多而且屬性之間的依賴關(guān)系有一些復(fù)雜而已。簡(jiǎn)單的來(lái)說(shuō)可以這么理解。
二、WindowManager介紹
上面簡(jiǎn)單介紹了懸浮窗的概念，而WindowManager是對(duì)懸浮窗進(jìn)行操作的一個(gè)媒介。
WindowManager是一個(gè)接口，他是繼承了ViewManager接口中的三個(gè)方法：
public interface ViewManager{ public void addView(View view, ViewGroup.LayoutParams params); public void updateViewLayout(View view, ViewGroup.LayoutParams params); public void removeView(View view);}windowManage暴露給我們的只是這個(gè)三個(gè)方法，真的是簡(jiǎn)單粗暴，但是很實(shí)用。
這三個(gè)方法看名字就知道含義了，增刪改嘛，就不多說(shuō)啦。
而在上面提到的對(duì)于懸浮窗的三種分類，也是WindowManager的內(nèi)部類：WindowManager.LayoutParams，關(guān)于LayoutParams是什么在這里就不多說(shuō)了。這不是我們的重點(diǎn)。
我們平時(shí)想要添加一個(gè)懸浮窗，就會(huì)使用第一個(gè)方法：
WindowManager windowManager = getWindowManager(); windowManager.addView(.....);
我們?cè)趃etWindowManager獲取的類，實(shí)際上是WindowManager的是WindowManager的實(shí)現(xiàn)類：WindowManagerImpl。接下來(lái)我們走一下添加懸浮窗的流程。
三、懸浮窗添加流程
入口肯定是從自己的addView中，上面說(shuō)到了WindowManager的實(shí)現(xiàn)類是WindowManagerImpl，來(lái)看一下：
@Override public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) { applyDefaultToken(params); mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow); }這里有兩步：第一步是給layoutparams設(shè)置一個(gè)默認(rèn)的令牌（就是token這個(gè)屬性，至于這個(gè)干什么的等會(huì)再說(shuō)）
private void applyDefaultToken(@NonNull ViewGroup.LayoutParams params) { // 設(shè)置條件：有默認(rèn)令牌，而且不是子窗口級(jí)別的懸浮窗 if (mDefaultToken != null && mParentWindow == null) { if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } // 如果沒(méi)有令牌就設(shè)置默認(rèn)令牌 final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params; if (wparams.token == null) { wparams.token = mDefaultToken; } } }然后調(diào)用了mGlobal的addView：
public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) { /**進(jìn)行一系列判空操作。。。**/ if (parentWindow != null) { 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; 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 { root.setView(view, wparams, panelParentView); } catch (RuntimeException e) { // BadTokenException or InvalidDisplayException, clean up. if (index >= 0) { removeViewLocked(index, true); } throw e; } } }看到WindowManagerGLobal中有三個(gè)屬性： mViews、mRoots、mParams，可以大膽猜測(cè)這個(gè)類中保存了我們進(jìn)程中的所有視圖以及相關(guān)屬性。在這里主要關(guān)注一下ViewRootImpl的這個(gè)實(shí)例對(duì)象root，接下來(lái)的會(huì)走進(jìn)root的setView中。
ViewRootImpl的setView方法內(nèi)容有點(diǎn)多，我這里就截取關(guān)鍵的兩部分：
1.
int res; /** = WindowManagerImpl.ADD_OKAY; **/ try { mOrigWindowType = mWindowAttributes.type; mAttachInfo.mRecomputeGlobalAttributes = true; collectViewAttributes(); res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(), mWinFrame, mAttachInfo.mContentInsets, mAttachInfo.mStableInsets, mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel);創(chuàng)建了一個(gè)名為res的int類型變量，他要獲取到的是懸浮窗添加的結(jié)果：成功或者失敗。
2.
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 typ + 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); }第二部分是res返回失敗的所有情況，在添加成功的時(shí)候res為OKAY，而非OKAY的情況就是上述情況。
接下來(lái)來(lái)看一下添加懸浮窗的操作，就是1中mWindowSession.addToDisplay。mWindowSession類型如下：
final IWindowSession mWindowSession;
在這里其實(shí)用到了aidl跨進(jìn)程通信，最終執(zhí)行該方法的類是Session：
@Override public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame, Rect outContentInsets, Rect outStableInsets, Rect outOutsets, DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) { return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outFrame, outContentInsets, outStableInsets, outOutsets, outDisplayCutout, outInputChannel); }這個(gè)mService就是一個(gè)關(guān)鍵了系統(tǒng)類——WindowMamagerService（WMS）。到了這里我們簡(jiǎn)單過(guò)一下思路：在addView之后，通過(guò)WindowManagerGlobal進(jìn)行一些相關(guān)配置，傳入ViewRootImpl，再通過(guò)aidl方式發(fā)送給WMS系統(tǒng)服務(wù)。
可能有小伙伴會(huì)疑惑。好端端的為什么要用aidl實(shí)現(xiàn)？最開(kāi)始本人也有這個(gè)疑惑，但是后來(lái)想了想所有的窗口無(wú)論系統(tǒng)窗口還是第三方app，窗口都是要通過(guò)一個(gè)類去進(jìn)行添加允許判斷，這里使用aidl是在合適不過(guò)的了。我們接著看一下WMS的addWindow方法：
這個(gè)addWindow方法又是一段超長(zhǎng)的代碼，所以也就不全粘，說(shuō)一下他的簡(jiǎn)單流程吧,主要是分為三步：權(quán)限判斷、條件篩選、添加窗口
WMS的addWindow方法：
int res = mPolicy.checkAddPermission(attrs, appOp); if (res != WindowManagerGlobal.ADD_OKAY) { return res; }首先進(jìn)行一個(gè)權(quán)限判斷，
final WindowManagerPolicy mPolicy;
WindowManagerPolicy的實(shí)現(xiàn)類是PhoneWindowManagerPolicy，看一下他的實(shí)現(xiàn)：
又是小一百行的代碼，我們拆開(kāi)來(lái)看：
//排除不屬于三種類型懸浮窗范圍內(nèi)的type //很明顯的三段排除。 if (!((type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) || (type >= FIRST_SUB_WINDOW && type <= LAST_SUB_WINDOW) || (type >= FIRST_SYSTEM_WINDOW && type <= LAST_SYSTEM_WINDOW))) { return WindowManagerGlobal.ADD_INVALID_TYPE; } //不是系統(tǒng)級(jí)別的懸浮窗直接滿足條件 if (type < FIRST_SYSTEM_WINDOW || type > LAST_SYSTEM_WINDOW) { return ADD_OKAY; } //以下幾種不是系統(tǒng)警告類型的系統(tǒng)彈窗，會(huì)滿足條件，除此之外的使用默認(rèn)判斷的方式 if (!isSystemAlertWindowType(type)) { switch (type) { case TYPE_TOAST: outAppOp[0] = OP_TOAST_WINDOW; return ADD_OKAY; case TYPE_DREAM: case TYPE_INPUT_METHOD: case TYPE_WALLPAPER: case TYPE_PRESENTATION: case TYPE_PRIVATE_PRESENTATION: case TYPE_VOICE_INTERACTION: case TYPE_ACCESSIBILITY_OVERLAY: case TYPE_QS_DIALOG: // The window manager will check these. return ADD_OKAY; } return mContext.checkCallingOrSelfPermission(INTERNAL_SYSTEM_WINDOW) == PERMISSION_GRANTED ? ADD_OKAY : ADD_PERMISSION_DENIED; }后面的幾段代碼會(huì)頻繁出現(xiàn)最后的這段代碼：mContext.checkCallingOrSelfPermission，具體實(shí)現(xiàn)的類是ContextFixture：
@Override public int checkCallingOrSelfPermission(String permission) { if (mPermissionTable.contains(permission) || mPermissionTable.contains(PERMISSION_ENABLE_ALL)) { logd("checkCallingOrSelfPermission: " + permission + " return GRANTED"); return PackageManager.PERMISSION_GRANTED; } else { logd("checkCallingOrSelfPermission: " + permission + " return DENIED"); return PackageManager.PERMISSION_DENIED; } }這里會(huì)使用默認(rèn)權(quán)限判斷的方式，要么允許對(duì)應(yīng)權(quán)限，要么就是擁有全部權(quán)限，否則就會(huì)返回DENIED。
這個(gè)說(shuō)完接著回到checkPermission方法。
//對(duì)于系統(tǒng)進(jìn)程直接滿足允許 final int callingUid = Binder.getCallingUid(); if (UserHandle.getAppId(callingUid) == Process.SYSTEM_UID) { return ADD_OKAY; }說(shuō)實(shí)話下面這一段代碼我看的不是很明白，只是看到了這里對(duì)8.0之后做了版本限制，直接使用默認(rèn)檢查方式。
ApplicationInfo appInfo; try { appInfo = mContext.getPackageManager().getApplicationInfoAsUser( attrs.packageName, 0 /* flags */, UserHandle.getUserId(callingUid)); } catch (PackageManager.NameNotFoundException e) { appInfo = null; } if (appInfo == null || (type != TYPE_APPLICATION_OVERLAY && appInfo.targetSdkVersion >= O)) { return (mContext.checkCallingOrSelfPermission(INTERNAL_SYSTEM_WINDOW) == PERMISSION_GRANTED) ? ADD_OKAY : ADD_PERMISSION_DENIED; }這段是要從PackageManager中獲取ApplicationInfo，如果獲取失敗會(huì)拋出NameNotFound異常。所以下面的判斷是在異常的時(shí)候使用默認(rèn)權(quán)限處理方式。
最后還以一步檢查操作，關(guān)系不大就不看了。到這里checkPermission方法就結(jié)束了。
權(quán)限檢查的步驟已經(jīng)結(jié)束，接著就是根據(jù)上述獲取到的結(jié)果進(jìn)行條件篩選。
if (res != WindowManagerGlobal.ADD_OKAY) { return res; }首先在權(quán)限檢查的步驟獲取權(quán)限失敗，那么會(huì)直接返回，不會(huì)執(zhí)行條件篩選的步驟。而真正的條件篩選步驟代碼也是很多，我這里直接粘過(guò)來(lái)然后說(shuō)了。
//111111111111111 if (!mDisplayReady) { throw new IllegalStateException("Display has not been initialialized"); } final DisplayContent displayContent = getDisplayContentOrCreate(displayId); if (displayContent == null) { Slog.w(TAG_WM, "Attempted to add window to a display that does not exist: " + displayId + ". Aborting."); return WindowManagerGlobal.ADD_INVALID_DISPLAY; } if (!displayContent.hasAccess(session.mUid) && !mDisplayManagerInternal.isUidPresentOnDisplay(session.mUid, displayId)) { Slog.w(TAG_WM, "Attempted to add window to a display for which the application " + "does not have access: " + displayId + ". Aborting."); return WindowManagerGlobal.ADD_INVALID_DISPLAY; } if (mWindowMap.containsKey(client.asBinder())) { Slog.w(TAG_WM, "Window " + client + " is already added"); return WindowManagerGlobal.ADD_DUPLICATE_ADD; } //22222222222222 if (type >= FIRST_SUB_WINDOW && type <= LAST_SUB_WINDOW) { parentWindow = windowForClientLocked(null, attrs.token, false); if (parentWindow == null) { Slog.w(TAG_WM, "Attempted to add window with token that is not a window: " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN; } if (parentWindow.mAttrs.type >= FIRST_SUB_WINDOW && parentWindow.mAttrs.type <= LAST_SUB_WINDOW) { Slog.w(TAG_WM, "Attempted to add window with token that is a sub-window: " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN; } } //333333333333333 if (type == TYPE_PRIVATE_PRESENTATION && !displayContent.isPrivate()) { Slog.w(TAG_WM, "Attempted to add private presentation window to a non-private display. Aborting."); return WindowManagerGlobal.ADD_PERMISSION_DENIED; } //444444444444444 AppWindowToken atoken = null; final boolean hasParent = parentWindow != null; // Use existing parent window token for child windows since they go in the same token // as there parent window so we can apply the same policy on them. WindowToken token = displayContent.getWindowToken( hasParent ? parentWindow.mAttrs.token : attrs.token); // If this is a child window, we want to apply the same type checking rules as the // parent window type. final int rootType = hasParent ? parentWindow.mAttrs.type : type; boolean addToastWindowRequiresToken = false; if (token == null) { if (rootType >= FIRST_APPLICATION_WINDOW && rootType <= LAST_APPLICATION_WINDOW) { Slog.w(TAG_WM, "Attempted to add application window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_INPUT_METHOD) { Slog.w(TAG_WM, "Attempted to add input method window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_VOICE_INTERACTION) { Slog.w(TAG_WM, "Attempted to add voice interaction window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_WALLPAPER) { Slog.w(TAG_WM, "Attempted to add wallpaper window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_DREAM) { Slog.w(TAG_WM, "Attempted to add Dream window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_QS_DIALOG) { Slog.w(TAG_WM, "Attempted to add QS dialog window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (rootType == TYPE_ACCESSIBILITY_OVERLAY) { Slog.w(TAG_WM, "Attempted to add Accessibility overlay window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } if (type == TYPE_TOAST) { // Apps targeting SDK above N MR1 cannot arbitrary add toast windows. if (doesAddToastWindowRequireToken(attrs.packageName, callingUid, parentWindow)) { Slog.w(TAG_WM, "Attempted to add a toast window with unknown token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } final IBinder binder = attrs.token != null ? attrs.token : client.asBinder(); final boolean isRoundedCornerOverlay = (attrs.privateFlags & PRIVATE_FLAG_IS_ROUNDED_CORNERS_OVERLAY) != 0; token = new WindowToken(this, binder, type, false, displayContent, session.mCanAddInternalSystemWindow, isRoundedCornerOverlay); } else if (rootType >= FIRST_APPLICATION_WINDOW && rootType <= LAST_APPLICATION_WINDOW) { atoken = token.asAppWindowToken(); if (atoken == null) { Slog.w(TAG_WM, "Attempted to add window with non-application token " + token + ". Aborting."); return WindowManagerGlobal.ADD_NOT_APP_TOKEN; } else if (atoken.removed) { Slog.w(TAG_WM, "Attempted to add window with exiting application token " + token + ". Aborting."); return WindowManagerGlobal.ADD_APP_EXITING; } else if (type == TYPE_APPLICATION_STARTING && atoken.startingWindow != null) { Slog.w(TAG_WM, "Attempted to add starting window to token with already existing" + " starting window"); return WindowManagerGlobal.ADD_DUPLICATE_ADD; } } else if (rootType == TYPE_INPUT_METHOD) { if (token.windowType != TYPE_INPUT_METHOD) { Slog.w(TAG_WM, "Attempted to add input method window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (rootType == TYPE_VOICE_INTERACTION) { if (token.windowType != TYPE_VOICE_INTERACTION) { Slog.w(TAG_WM, "Attempted to add voice interaction window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (rootType == TYPE_WALLPAPER) { if (token.windowType != TYPE_WALLPAPER) { Slog.w(TAG_WM, "Attempted to add wallpaper window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (rootType == TYPE_DREAM) { if (token.windowType != TYPE_DREAM) { Slog.w(TAG_WM, "Attempted to add Dream window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (rootType == TYPE_ACCESSIBILITY_OVERLAY) { if (token.windowType != TYPE_ACCESSIBILITY_OVERLAY) { Slog.w(TAG_WM, "Attempted to add Accessibility overlay window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (type == TYPE_TOAST) { // Apps targeting SDK above N MR1 cannot arbitrary add toast windows. addToastWindowRequiresToken = doesAddToastWindowRequireToken(attrs.packageName, callingUid, parentWindow); if (addToastWindowRequiresToken && token.windowType != TYPE_TOAST) { Slog.w(TAG_WM, "Attempted to add a toast window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (type == TYPE_QS_DIALOG) { if (token.windowType != TYPE_QS_DIALOG) { Slog.w(TAG_WM, "Attempted to add QS dialog window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } } else if (token.asAppWindowToken() != null) { Slog.w(TAG_WM, "Non-null appWindowToken for system window of rootType=" + rootType); // It is not valid to use an app token with other system types; we will // instead make a new token for it (as if null had been passed in for the token). attrs.token = null; token = new WindowToken(this, client.asBinder(), type, false, displayContent, session.mCanAddInternalSystemWindow); } //5555555555555 final WindowState win = new WindowState(this, session, client, token, parentWindow, appOp[0], seq, attrs, viewVisibility, session.mUid, session.mCanAddInternalSystemWindow); if (win.mDeathRecipient == null) { // Client has apparently died, so there is no reason to // continue. Slog.w(TAG_WM, "Adding window client " + client.asBinder() + " that is dead, aborting."); return WindowManagerGlobal.ADD_APP_EXITING; } if (win.getDisplayContent() == null) { Slog.w(TAG_WM, "Adding window to Display that has been removed."); return WindowManagerGlobal.ADD_INVALID_DISPLAY; } final boolean hasStatusBarServicePermission = mContext.checkCallingOrSelfPermission(permission.STATUS_BAR_SERVICE) == PackageManager.PERMISSION_GRANTED; mPolicy.adjustWindowParamsLw(win, win.mAttrs, hasStatusBarServicePermission); win.setShowToOwnerOnlyLocked(mPolicy.checkShowToOwnerOnly(attrs)); res = mPolicy.prepareAddWindowLw(win, attrs); if (res != WindowManagerGlobal.ADD_OKAY) { return res; } final boolean openInputChannels = (outInputChannel != null && (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0); if (openInputChannels) { win.openInputChannel(outInputChannel); } //666666666666666 if (type == TYPE_TOAST) { if (!getDefaultDisplayContentLocked().canAddToastWindowForUid(callingUid)) { Slog.w(TAG_WM, "Adding more than one toast window for UID at a time."); return WindowManagerGlobal.ADD_DUPLICATE_ADD; } if (addToastWindowRequiresToken || (attrs.flags & LayoutParams.FLAG_NOT_FOCUSABLE) == 0 || mCurrentFocus == null || mCurrentFocus.mOwnerUid != callingUid) { mH.sendMessageDelayed( mH.obtainMessage(H.WINDOW_HIDE_TIMEOUT, win), win.mAttrs.hideTimeoutMilliseconds); } }這里講篩選部分大體分成這么幾個(gè)步驟：
在代碼中對(duì)應(yīng)的步驟有明確的標(biāo)注，而具體的代碼大多只是一些判斷，所以在感覺(jué)沒(méi)有細(xì)說(shuō)的必要了。
在條件篩選完成之后，剩下的類型都是符合添加的類型，從現(xiàn)在開(kāi)始就開(kāi)始對(duì)不同的type進(jìn)行不同的添加。經(jīng)過(guò)多到加工后，將OKAY返回。
如果能從添加窗口的步驟返回，就說(shuō)明一定是OKAY的。那么我們可以一步步跳回層層調(diào)用的代碼，最終在ViewRootImpl中，對(duì)沒(méi)有添加成功的拋出異常。
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); }對(duì)于OKAY的，在ViewRootImpl中會(huì)做一些其他的操作，反正我是沒(méi)看懂-。=、
四、小結(jié)
到這里WMS的添加懸浮窗口的流程差不多就過(guò)了一遍了。可能有些地方說(shuō)的不是很細(xì)，大家下來(lái)可以關(guān)注一下個(gè)別幾個(gè)點(diǎn)。整個(gè)過(guò)程有這么幾個(gè)需要強(qiáng)調(diào)的地方。
如果在添加懸浮窗的時(shí)候使用了不同的type，可能會(huì)發(fā)生異常：本人拿了一個(gè)8.0的手機(jī)，分別對(duì)窗口type設(shè)置為OVERLAY和ERROR。因?yàn)镋RROR類型是被棄用的，我發(fā)現(xiàn)使用ERROR會(huì)拋出異常，而OVERLAY不會(huì)。同樣的拿了一個(gè)6.0的手機(jī)添加ERROR類型就沒(méi)有異常拋出，肯定是上述的問(wèn)題導(dǎo)致的，但是具體在哪一塊我還沒(méi)有找到，因?yàn)檎麄€(gè)流程的出口太多了-。=。
此外在WindowManagerGlobal.addView方法中，有一個(gè)地方：
if (parentWindow != null) { parentWindow.adjustLayoutParamsForSubWindow(wparams); } else {這個(gè)方法是對(duì)于有子窗口類型的證書處理，網(wǎng)上查了一下該方法在四點(diǎn)幾、六點(diǎn)幾和8.0是不同的，也就是說(shuō)對(duì)證書的處理方式變化了，這里本人還沒(méi)有細(xì)看，有興趣的盆友可以研究一下然后評(píng)論交流一番。
總結(jié)
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