本文来自http://blog.csdn.net/liuxian13183/ ，引用必须注明出处！
关于Framework，就是应用层底下的控制层，离应用层最近，总想找个机会，写写WindowMangerService和ActivityManagerService（注意非控件，而是指一类服务）以及其他一些东西，对底层做一个更为全面的认识。而很早以前，写过一篇文章，来简述Android系统-" Android高级之系统介绍"，同样今天我们在讲Framework层时也会再对系统做一个回顾；下图是我对本节内容的一个基本介绍。
PS:W类是ViewRoot的一个内部类，ViewRoot最大作用就是把IPC调用转为本地调用。
HistoryRecord-每个Acitivty都会有一个，用来管理和记录Activity，是一个Binder对象
ViewRoot-实现View和WindowManger之间的协议，是View Hierarchy的最顶层
PhoneWindow-其中有autoManger和keyguardManager的实现对象
一、窗口
就着上图，我们会对每一条做进一步的解说（注意上图大多是包含关系，少数是关联关系，请区别对待），上图对Framework简单做了描述；同时科普一下什么叫窗口，窗口非指window类，而是指所有使用windowmanger将
其展示在用户面前的控件，如toast、activity、menu等，而这些界面通过设置window的callback来监听到wms传给view对象的信息，如手势操作。而窗口类型基本可以分为3种：
1、系统窗口，不需要父窗口-可以指定2000-2999层
2、子窗口，依赖父窗口-1000-1999层 如Toast
3、应用窗口，对应activity-小于99层 如Activity
窗口可以说是View，而wms不直接跟view沟通，而是通过实现IWindow的ViewRoot.W类，然后再传给view。
关于Context，上下文引用，项目中使用的还比较多，是一个场景，用来配合上下文操作；一个应用中context的数量=service个数+activity个数+application个数，原因它们都继承自ContextWraper，而它继承自context。
二、linux文件系统
由于android系统基于linux，就先讲一下linux基础，文件系统通常有3个特点：
1、由文件和目录组成，占据一定存储空间
2、具有读、写、执行权限，可以复制和移动
3、多个文件系统可以并列，且类型可以不同，如FAT16和NTFS
主要的文件目录有以下几种-与android系统类比：
1、bin，存放用户级二进制工具-相当于android系统的acct目录
2、boot，内核镜像文件，由bootloader装载-firmware
3、dev，各种文件系统如打印机等-相当于android系统的dev目录+storage+mnt/sdcard
4、etc，配置文件区-相当于android系统的config目录
5、home，用户工作目录-data/user
6、lib，系统运行时库的存放地-data/app-lib
7、opt，存放系统程序-data/app-private
8、proc，系统级如内核和进程所在文件-proc目录
9、root，管理员工作目录-root目录
10、sbin，管理员的二进制工具-sbin目录
11、sys，驱动对应的系统文件如固件、内核、电量等-sys目录+system目录
12、usr，应用程序安装区-data/app
13、var，调试信息等-data/anr等
因此从上面来以看出，其实操作系统都是由文件组成，外加一些硬件感应设备。但上面介绍的依然不全面，因为android是一层套一层，资源是总体一致，大体分散的结构。同时上面会涉及到进程pid，值为100以内是系统进程，1000以内是root进程，1000以上是用户进程。讲完目录，咱们再讲讲命令：
1、man，查询某命令的意思
2、ls，列出当前目录下所有文件及文件夹信息
3、find，用名字查找文件信息
4、grep，查询文件中的字符串信息
5、cat，打开文件
6、chmod，指定权限，ugo指user（自身）、group（组）、other（其他），权限有r（读1）w（写2）x（执行4），指定权限有两种方式如chmod ug+x（给予当前用户和某群组执行的权限），chmod 777（给予三者所有权限，原因请看上一行）
7、ps和kill，ps列出当前所有进程，kill杀死某进程
8、export，用于设置变量作用于全局
9、mount和unmount，加载和卸载文件系统
好在用过linux操作系统工作过一段时间，对后来做Android开发，起到很大的帮助，上面介绍的是一些常用命令，有兴趣的可以安装一个linux系统来用，之前有一个同事使用ubuntu来编译so，而我当年用的是小红帽rethat。
三、linux启动过程
下面简单讲一个linux启动过程，其实Dalvik虚拟机也是类似
上图少说一点，在CPU运行之前，要把磁盘和其他内存启动，这样才能保证系统正式开始，因为所有系统均为文件，加载文件的硬盘不启，系统如何能被启动?
四、异步信息系统
在Android系统中，用的最多的设计模式就是handler+looper+messageQueue，无论在系统层还是在应用层，
之后我们会再讲到都被用烂了，异步线程表现为：开启后无限循环，遍历数据，如果为空则等待，直到下次数据不
为空时，使用场景有二
1、任务要常驻
2、任务需要根据消息来做不同操作
使用方法如上，解释几点，上面的数据指messegeQueue属于队列LILO，读/写数据时会加锁；如何应用呢，
Handler handler =new Handler(); 首先创建handler时，一般需要在UI线程中（一般你也没必要在子线程重写
handler），获得一个UI线程的looper对象；looper对象通过prepare方法（仅一次）准备一个MessageQueue
（系统唯一），调用loop方法一直分发消息；MessageQueue可以定义消息处理时刻，否则先进先出，
通过next和enquenceMessage方法来取和加入消息，处于wait状态则唤醒，若无消息则挂起。
五、Binder
再讲一个知识点Binder，然后结束本篇。
Binder工作在linux层面，是一小段内存，属于驱动，主要用来解决IPC调用，应用框架包括3部分
1、服务端接口-Binder对象，收到消息即启动隐藏线程，执行onTransact函数初始化；向客户端发送消息时，
挂起当前线程。
2、Binder驱动-创造mRemote的Binder对象，重载以下方法
1）以线程间消息通信模式，向服务端发送参数
2）挂起客户端线程，等待服务端返回处理结果，并通知客户端
3）接收服务端通知，继续执行客户端线程
3、客户端接口-向客户端发送消息，挂起当前线程。
Binder服务的设计原则是，开放ServiceManger接口给外界，关于具体的操作由底层去统一执行，不暴露出来，
这也是保证框架稳定、逻辑正确的重要方式，使不同管理类与底层实现可以分离解耦。
另一篇关于Binder介绍，最下面：http://blog.csdn.net/reboot123/article/details/52370416
下面这篇文章底层就是使用binder进行通信
六、token
token原意指口令，在这里指“身份证”，代表唯一性和代理性；一般token为IBind的实现类，即使View.Attach
Info中也是用IBind实现类来进行IPC调用。应用窗口一般都有token，而window可能没有，为什么？window可以不
对应此窗口存在。
应用窗口的token：一般最初跟window一样最终指向DecorView的W类，初始值是window的mAppToken，指应用
HistoryRecord。Activity的token起始是HistoryRecord，最终指向此W类即mAppToken，与window相同。
子窗口的token：是父窗口view的W类，即mPanelParentWindowToken
系统窗口无token
因此view中会有window的token，也会有父窗口的token，而每个应用窗口随activity诞生，均会有一个Activity
Thread陪伴。
PopupWindow上套PopupWindow，报错：unable to add window ,is your activity running ?
经查在windowManager执行addView操作时出错
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}
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");
}
// 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;
}
}ViewRootImpl出错出现ADD_BAD_APP_TOKEN或ADD_BAD_SUBWINDOW_TOKEN，要查WindowSession.addToDisplay
/**
* We have one child
*/
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
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.
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();
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, 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);
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);
}
}
}
WindowSession
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets,
InputChannel outInputChannel) {
return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,
outContentInsets, outStableInsets, outInputChannel);
}
WindowManagerService
public int addWindow(Session session, IWindow client, int seq,
WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
InputChannel outInputChannel) {
int[] appOp = new int[1];
int res = mPolicy.checkAddPermission(attrs, appOp);
if (res != WindowManagerGlobal.ADD_OKAY) {
return res;
}
boolean reportNewConfig = false;
WindowState attachedWindow = null;
long origId;
final int type = attrs.type;
synchronized(mWindowMap) {
if (!mDisplayReady) {
throw new IllegalStateException("Display has not been initialialized");
}
final DisplayContent displayContent = getDisplayContentLocked(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)) {
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;
}
if (type >= FIRST_SUB_WINDOW && type <= LAST_SUB_WINDOW) {
attachedWindow = windowForClientLocked(null, attrs.token, false);
if (attachedWindow == 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 (attachedWindow.mAttrs.type >= FIRST_SUB_WINDOW
&& attachedWindow.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;
}
}
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;
}
boolean addToken = false;
WindowToken token = mTokenMap.get(attrs.token);
AppWindowToken atoken = null;
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;
}
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_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;
}
if (addToken) {
mTokenMap.put(attrs.token, token);
}
win.attach();
mWindowMap.put(client.asBinder(), win);
if (win.mAppOp != AppOpsManager.OP_NONE) {
int startOpResult = mAppOps.startOpNoThrow(win.mAppOp, win.getOwningUid(),
win.getOwningPackage());
if ((startOpResult != AppOpsManager.MODE_ALLOWED) &&
(startOpResult != AppOpsManager.MODE_DEFAULT)) {
win.setAppOpVisibilityLw(false);
}
}
Binder.restoreCallingIdentity(origId);
return res;
}如果加入成功(mWindowMap.put（attr.token,token）)，则子View与父View建立连接关系。
查到mTokenMap.get(attr.token)为null，同时又是子窗口，因此报错。
至于为什么是null，继续
回到PopupWindow
public void showAsDropDown(View anchor, int xoff, int yoff, int gravity) {
if (isShowing() || mContentView == null) {
return;
}
TransitionManager.endTransitions(mDecorView);
attachToAnchor(anchor, xoff, yoff, gravity);
mIsShowing = true;
mIsDropdown = true;
final WindowManager.LayoutParams p = createPopupLayoutParams(anchor.getWindowToken());
preparePopup(p);
final boolean aboveAnchor = findDropDownPosition(anchor, p, xoff, yoff,
p.width, p.height, gravity);
updateAboveAnchor(aboveAnchor);
p.accessibilityIdOfAnchor = (anchor != null) ? anchor.getAccessibilityViewId() : -1;
invokePopup(p);
}
可以看到，二次添加的PopupWidow，使用一次添加的PopupWindow对象的token，而此token为
private int mWindowLayoutType = WindowManager.LayoutParams.TYPE_APPLICATION_PANEL;
private WindowManager.LayoutParams createPopupLayoutParams(IBinder token) {
final WindowManager.LayoutParams p = new WindowManager.LayoutParams();
// These gravity settings put the view at the top left corner of the
// screen. The view is then positioned to the appropriate location by
// setting the x and y offsets to match the anchor's bottom-left
// corner.
p.gravity = computeGravity();
p.flags = computeFlags(p.flags);
p.type = mWindowLayoutType;
p.token = token;
p.softInputMode = mSoftInputMode;
p.windowAnimations = computeAnimationResource();
return p;
}
但在WindowManagerService里，PopupWindow依赖show的控件是传过来的，而一次PopupWindow的type刚好等于
/**
* Window type: a panel on top of an application window. These windows
* appear on top of their attached window.
*/
public static final int TYPE_APPLICATION_PANEL = FIRST_SUB_WINDOW;所在WindowManagerService不允许在子窗口上创建子窗口。
if (type >= FIRST_SUB_WINDOW && type <= LAST_SUB_WINDOW) {
attachedWindow = windowForClientLocked(null, attrs.token, false);
if (attachedWindow == 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 (attachedWindow.mAttrs.type >= FIRST_SUB_WINDOW
&& attachedWindow.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;
}
}
完。
补充：Dialog则无此限制
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;
}
WindowManager.LayoutParams l = mWindow.getAttributes();
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {
WindowManager.LayoutParams nl = new WindowManager.LayoutParams();
nl.copyFrom(l);
nl.softInputMode |=
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
l = nl;
}
mWindowManager.addView(mDecor, l);
mShowing = true;
sendShowMessage();
}
Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
final Window w = new PhoneWindow(mContext);
mWindow = w;
}
PhoneWindow
public final WindowManager.LayoutParams getAttributes() {
return mWindowAttributes;
}
private final WindowManager.LayoutParams mWindowAttributes =
new WindowManager.LayoutParams();
public LayoutParams() {
super(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
type = TYPE_APPLICATION;
format = PixelFormat.OPAQUE;
}
public static final int TYPE_APPLICATION = 2;
WindowManagerService要求大于等1000，小于等于1999才报ADD_BAD_SUB_WINDOW。
因此Dialog无此限制。
Android的安装过程：http://www.2cto.com/kf/201402/280725.html
Binder能支持跨进程通信的原因，是它实现IBinder接口，系统定义实现此接口即赋予进程通信的功能。
优势：做数据拷贝只用一次，则Pipe、Socket都需要两次；其次安全性高，不会像Socket会暴露地址，被人替换；
通信机制：Service向ServiceManager注册，得到虚拟的Uid和Pid，使用Binder通信；Client向ServiceManager请求，得到虚拟的Uid和Pid，以及目标对象的Proxy，底层通过硬件协议传输，使用Binder通讯。
通信时Client手持Proxy，ServiceManger进行转换，调用到Service。三者运行在三个独立进程中。Client/Sever全双工，互为Sever/Client
实际案例：
Vivo7.0以上手机，无法弹出自定义Toast(WindowManager通过addView方式，再配合动画)，由于Android手机系统权限逐步收紧，导致无法成功申请的“SYSTEM_ALERT_WINDOW”权限。
解决思路：先看权限是否被收回，其次看使用系统Toast是否可行，最后尝试降级使用WindowManager。
解决办法，降低WindowManager.LayoutParam的flag等级，使用2000以下的等级，比如LAST_SUB_WINDOW（次级window1999）
