近期碰到了一个费解的bug，一个自定义的dialog库在新写的demo上运行总是崩溃，报出WindowManager$BadTokenException，可是在其他项目里都是正常的，很是费解，于是我一步一步的分析出问题所在。
1.错误分析
首先贴上错误日志，如图：
error1.png
看到这个exception，还是很常见的，经常在一些弹框上出现。出现原因可能有：
- 弹框弹出时，activity已经销毁了
- 使用的是Application的context
但根据后面描述，应该是activity没运行。于是我去检查了我的dialog弹出时机，并没有在activity销毁时弹出。我这边的代码看不出来什么问题，所以我觉得得往问题的源头开始找起。
2.从源码追踪
打开androidxref，搜索下报错的源头ViewRootImpl。我的手机是8.0的，所以选择此版本的源代码。
/frameworks/base/core/java/android/view/ViewRootImpl.java
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
... 省略无关代码
int res; /* = WindowManagerImpl.ADD_OKAY; */
requestLayout();
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
} catch (RemoteException e) {
} finally {
if (restore) {
attrs.restore();
}
}
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?");
}
throw new RuntimeException(
"Unable to add window -- unknown error code " + res);
}
}
}
}
可以看到根据mWindowSession.addToDisplay的返回值，抛出了这个exception,找下mWindowSession的初始化地方。
public ViewRootImpl(Context context, Display display) {
mContext = context;
mWindowSession = WindowManagerGlobal.getWindowSession();
mDisplay = display;
...
}
继续去看WindowManagerGlobal
/frameworks/base/core/java/android/view/WindowManagerGlobal.java
public static IWindowManager getWindowManagerService() {
synchronized (WindowManagerGlobal.class) {
if (sWindowManagerService == null) {
//此处使用aidl获得IWindowManager实例
sWindowManagerService = IWindowManager.Stub.asInterface(
ServiceManager.getService("window"));
try {
sWindowManagerService = getWindowManagerService();
ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
return sWindowManagerService;
}
}
啊哦，原来是通过aidl返回的WindowManagerService,好的离真相更近了，继续！找到WindowManagerService
/frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
@Override
public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client,
IInputContext inputContext) {
if (client == null) throw new IllegalArgumentException("null client");
if (inputContext == null) throw new IllegalArgumentException("null inputContext");
Session session = new Session(this, callback, client, inputContext);
return session;
}
可以看到是返回的Session对象。
/frameworks/base/services/core/java/com/android/server/wm/Session.java
让我们再看下Session的addToDisplay方法
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets,
Rect outOutsets, InputChannel outInputChannel) {
return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,
outContentInsets, outStableInsets, outOutsets, outInputChannel);
}
终于看到了罪魁祸首是谁了，这个mService就是WindowManagerService的实例。让我们看下到底为什么他要抛出异常，走进它的addWindow方法。
/frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public int addWindow(Session session, IWindow client, int seq,
WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
InputChannel outInputChannel) {
//省略大量多余代码
if (token == null) {
if (type >= FIRST_APPLICATION_WINDOW && type <= 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 (type == 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 (type == 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 (type == TYPE_WALLPAPER) {
Slog.w(TAG_WM, "Attempted to add wallpaper window with unknown token "
+ attrs.token + ". Aborting.");
return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
}
if (type == TYPE_DREAM) {
Slog.w(TAG_WM, "Attempted to add Dream window with unknown token "
+ attrs.token + ". Aborting.");
return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
}
if (type == 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 (type == 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,
attachedWindow)) {
Slog.w(TAG_WM, "Attempted to add a toast window with unknown token "
+ attrs.token + ". Aborting.");
return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
}
}
token = new WindowToken(this, attrs.token, -1, false);
addToken = true;
} else if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {
atoken = token.appWindowToken;
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;
}
if (type == TYPE_APPLICATION_STARTING && atoken.firstWindowDrawn) {
// No need for this guy!
if (DEBUG_STARTING_WINDOW || localLOGV) Slog.v(
TAG_WM, "**** NO NEED TO START: " + attrs.getTitle());
return WindowManagerGlobal.ADD_STARTING_NOT_NEEDED;
}
} else if (type == 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 (type == 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 (type == 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 (type == 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 (type == 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) {
//就是这里导致的这次崩溃
// Apps targeting SDK above N MR1 cannot arbitrary add toast windows.
addToastWindowRequiresToken = doesAddToastWindowRequireToken(attrs.packageName,
callingUid, attachedWindow);
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.appWindowToken != null) {
Slog.w(TAG_WM, "Non-null appWindowToken for system window of type=" + type);
// 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, null, -1, false);
addToken = true;
}
}
Binder.restoreCallingIdentity(origId);
return res;
}
可能导致之前的异常的是ADD_BAD_APP_TOKEN和ADD_BAD_SUBWINDOW_TOKEN,引起这2个的有不少，一个一个看下去。终于找到一个可能的原因。
Apps targeting SDK above N MR1 cannot arbitrary add toast windows.
原来targetSdkVersion在安卓7.1以上的版本都不能添加此type。看下我们app的版本，竟然是27。emmm，调低到24。运行,my god！成功了，哈哈。
3.总结
原来原因是这么的简单，只是targetSdkVersion指定太高，我们来看下安卓中常见的几个版本：
- minSdkVersion：用于指定app最低兼容的系统版本，低于此版本的系统将无法安装此app
- targetSdkVersion：通俗的来说就是兼容版本，由于安卓系统会更新，每个版本都会向前兼容。如果当前系统版本高于你的targetSdkVersion，就会去使用兼容方案。当然取较高的版本也可以使用最新的特性。
可以看到targetSdkVersion还是不宜太高，不然很多兼容方案都不会使用，导致各种错误。
题外话
其实这个targetSdkVersion是我建玩工程后，忘了改。用android新建工程时总会采用最高版本，我不经想到，能不能不要每次都手动改。
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