1.WMS概述
WMS是系统的其他服务，无论对于应用开发还是Framework开发都是重点的知识，它的职责有很多，主要有以下几点：
窗口管理
WMS是窗口的管理者，它负责窗口的启动、添加和删除，另外窗口的大小和层级也是由WMS进行管理的。窗口管理的核心成员有DisplayContent、WindowToken和WindowState。
窗口动画
窗口间进行切换时，使用窗口动画可以显得更炫一些，窗口动画由WMS的动画子系统来负责，动画子系统的管理者为WindowAnimator。
输入系统的中转站
通过对窗口的触摸从而产生触摸事件，InputManagerService（IMS）会对触摸事件进行处理，它会寻找一个最合适的窗口来处理触摸反馈信息，WMS是窗口的管理者，因此，WMS“理所应当”的成为了输入系统的中转站。
Surface管理
窗口并不具备有绘制的功能，因此每个窗口都需要有一块Surface来供自己绘制。为每个窗口分配Surface是由WMS来完成的。
WMS的职责可以简单总结为下图。
2.windowState
windowState就是window，每个window都有一个surface来绘画，window本身是没法画的。
Window的类型
Android系统的Window有很多个，大体上来说，Framework定义了三种窗口类型；
系统Window
常见的系统Window有哪些呢？比如在手机电量低的时候，会有一个提示电量低的Window,我们输入文字的时候，会弹出输入法Window,还有搜索条Window,来电显示Window,Toast对应的Window,可以总结出来，系统Window是独立与我们的应用程序的，对于应用程序而言，我们理论上是无法创建系统Window，因为没有权限，这个权限只有系统进程有。
应用程序Window
所谓应用窗口指的就是该窗口对应一个Activity，因此，要创建应用窗口就必须在Activity中完成了。本节后面会分析Activity对应的Window的创建过程。
子Window
所谓的子Window，是说这个Window必须要有一个父窗体，比如PopWindow，Dialog是属于应用程序Window,这个比较特殊。
每一种窗口类型定义了一种对应的type
应用类型的窗口的type范围是１~99
应用类型的窗口
子窗口的type范围是1000~1999
子窗口
系统的窗口的type范围是2000以上
系统的窗口
系统窗口的type值>子窗口的type值>应用类型窗口的type值，一般来说，根据type值大小关系，可以推出系统窗口在子窗口的上面，子窗口在应用窗口的上面。
3.z-order
手机上采用的是层叠式布局，层叠式布局是一个三维的空间，将手机的水平方向作为Ｘ轴，竖直方向作为Ｙ轴，还有一根垂直与屏幕从里朝外方向的虚拟的Z轴，所有窗口 (WindowState) 按照顺序排列在Ｚ轴上，如下图。z轴坐标就是z-order，越大证明他的windowState越在前面。
3.1 、 mBaseLayer 主序 确认
@/frameworks/base/services/core/java/com/android/server/wm/WindowState.java
WindowState(WindowManagerService service, Session s, IWindow c, WindowToken token,
WindowState parentWindow, int appOp, int seq, WindowManager.LayoutParams a,
int viewVisibility, int ownerId, boolean ownerCanAddInternalSystemWindow,
PowerManagerWrapper powerManagerWrapper) {
...
if (mAttrs.type >= FIRST_SUB_WINDOW && mAttrs.type <= LAST_SUB_WINDOW) {
// The multiplier here is to reserve space for multiple
// windows in the same type layer.
mBaseLayer = mPolicy.getWindowLayerLw(parentWindow //mBaseLayer 主序
* TYPE_LAYER_MULTIPLIER + TYPE_LAYER_OFFSET; TYPE_LAYER_MULTIPLIER = 10000 TYPE_LAYER_OFFSET = 1000
mSubLayer = mPolicy.getSubWindowLayerFromTypeLw(a.type); //mSubLayer 次序
mIsChildWindow = true;
if (DEBUG_ADD_REMOVE) Slog.v(TAG, "Adding " + this + " to " + parentWindow);
parentWindow.addChild(this, sWindowSubLayerComparator);
mLayoutAttached = mAttrs.type !=
WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG;
mIsImWindow = parentWindow.mAttrs.type == TYPE_INPUT_METHOD
|| parentWindow.mAttrs.type == TYPE_INPUT_METHOD_DIALOG;
mIsWallpaper = parentWindow.mAttrs.type == TYPE_WALLPAPER;
} else {
// The multiplier here is to reserve space for multiple
// windows in the same type layer.
mBaseLayer = mPolicy.getWindowLayerLw(this)
* TYPE_LAYER_MULTIPLIER + TYPE_LAYER_OFFSET;
mSubLayer = 0;
mIsChildWindow = false;
mLayoutAttached = false;
mIsImWindow = mAttrs.type == TYPE_INPUT_METHOD
|| mAttrs.type == TYPE_INPUT_METHOD_DIALOG;
mIsWallpaper = mAttrs.type == TYPE_WALLPAPER;
}
...
}mBaseLayer =窗口类型×10000+1000,窗口类型判断如下
default int getWindowLayerFromTypeLw(int type, boolean canAddInternalSystemWindow) {
if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {
return APPLICATION_LAYER;
}
switch (type) {
case TYPE_WALLPAPER:
// wallpaper is at the bottom, though the window manager may move it.
return 1;
case TYPE_PRESENTATION:
case TYPE_PRIVATE_PRESENTATION:
return APPLICATION_LAYER;
case TYPE_DOCK_DIVIDER:
return APPLICATION_LAYER;
case TYPE_QS_DIALOG:
return APPLICATION_LAYER;
case TYPE_PHONE:
return 3;
case TYPE_SEARCH_BAR:
case TYPE_VOICE_INTERACTION_STARTING:
return 4;
case TYPE_VOICE_INTERACTION:
// voice interaction layer is almost immediately above apps.
return 5;
case TYPE_INPUT_CONSUMER:
return 6;
case TYPE_SYSTEM_DIALOG:
return 7;
case TYPE_TOAST:
// toasts and the plugged-in battery thing
return 8;
case TYPE_PRIORITY_PHONE:
// SIM errors and unlock. Not sure if this really should be in a high layer.
return 9;
case TYPE_SYSTEM_ALERT:
// like the ANR / app crashed dialogs
return canAddInternalSystemWindow ? 11 : 10;
case TYPE_APPLICATION_OVERLAY:
return 12;
case TYPE_DREAM:
// used for Dreams (screensavers with TYPE_DREAM windows)
return 13;
case TYPE_INPUT_METHOD:
// on-screen keyboards and other such input method user interfaces go here.
return 14;
case TYPE_INPUT_METHOD_DIALOG:
// on-screen keyboards and other such input method user interfaces go here.
return 15;
case TYPE_STATUS_BAR:
return 17;
case TYPE_STATUS_BAR_PANEL:
return 18;
case TYPE_STATUS_BAR_SUB_PANEL:
return 19;
case TYPE_KEYGUARD_DIALOG:
return 20;
case TYPE_VOLUME_OVERLAY:
// the on-screen volume indicator and controller shown when the user
// changes the device volume
return 21;
case TYPE_SYSTEM_OVERLAY:
// the on-screen volume indicator and controller shown when the user
// changes the device volume
return canAddInternalSystemWindow ? 22 : 11;
case TYPE_NAVIGATION_BAR:
// the navigation bar, if available, shows atop most things
return 23;
case TYPE_NAVIGATION_BAR_PANEL:
// some panels (e.g. search) need to show on top of the navigation bar
return 24;
case TYPE_SCREENSHOT:
// screenshot selection layer shouldn't go above system error, but it should cover
// navigation bars at the very least.
return 25;
case TYPE_SYSTEM_ERROR:
// system-level error dialogs
return canAddInternalSystemWindow ? 26 : 10;
case TYPE_MAGNIFICATION_OVERLAY:
// used to highlight the magnified portion of a display
return 27;
case TYPE_DISPLAY_OVERLAY:
// used to simulate secondary display devices
return 28;
case TYPE_DRAG:
// the drag layer: input for drag-and-drop is associated with this window,
// which sits above all other focusable windows
return 29;
case TYPE_ACCESSIBILITY_OVERLAY:
// overlay put by accessibility services to intercept user interaction
return 30;
case TYPE_SECURE_SYSTEM_OVERLAY:
return 31;
case TYPE_BOOT_PROGRESS:
return 32;
case TYPE_POINTER:
// the (mouse) pointer layer
return 33;
default:
Slog.e("WindowManager", "Unknown window type: " + type);
return APPLICATION_LAYER;
}
}3.2 、mSubLayer 子序的确认
SubLayer(称为子序)，SubLayer值是用来描述一个窗口是否属于另外一个窗口的子窗口，或者说SubLayer值是用来确定子窗口和父窗口之间的相对位置的。
一个Activity中有三个子窗口WindowState1、WindowState２、WindowState３，WindowState1WindowState２在窗口Ａ的前面，WindowState３在Ａ的后面，这几个兄弟窗口为什么可以这样排序呢，这就是mSubLayer的作用，子序越大，则相对其他兄弟窗口越靠前，反之，越靠后，如果为负数，就处在父窗口的后面，如窗口Ａ中的WindowState3，子序是根据窗口类型调用subWindowTypeToLayerLw确定的，subWindowTypeToLayerLw同样是在Window的构造方法中调用的。
public int subWindowTypeToLayerLw(int type) {
switch (type) {
case TYPE_APPLICATION_PANEL:
case TYPE_APPLICATION_ATTACHED_DIALOG:
return APPLICATION_PANEL_SUBLAYER;//返回值是1
case TYPE_APPLICATION_MEDIA:
return APPLICATION_MEDIA_SUBLAYER;//返回值是-2
case TYPE_APPLICATION_MEDIA_OVERLAY:
return APPLICATION_MEDIA_OVERLAY_SUBLAYER;//返回值是-1
case TYPE_APPLICATION_SUB_PANEL:
return APPLICATION_SUB_PANEL_SUBLAYER;//返回值是2
case TYPE_APPLICATION_ABOVE_SUB_PANEL:
return APPLICATION_ABOVE_SUB_PANEL_SUBLAYER;//返回值是3
}
Log.e(TAG, "Unknown sub-window type: " + type);
return 0;
}3.3 、窗口Z序的调整
当WindowState创建完成，并且被添加到WMS维持的数组里面后，就需要调用WindowLayersController的assignLayersLocked(windows)，进行Z序的调整。
//参数windows是窗口列表
final void assignLayersLocked(WindowList windows) {
if (DEBUG_LAYERS) Slog.v(TAG_WM, "Assigning layers based on windows=" + windows,
new RuntimeException("here").fillInStackTrace());
clear();
int curBaseLayer = 0;
int curLayer = 0;
boolean anyLayerChanged = false;
//遍历窗口列表，上面通过Z序的计算公式计算出来的Z序值保存在WindowState的变量mBaseLayer
中，这个循环的意思是，遇到同类型的窗口，后一个窗口在前一个窗口的基础上偏移５。
for (int i = 0, windowCount = windows.size(); i < windowCount; i++) {
final WindowState w = windows.get(i);
boolean layerChanged = false;
int oldLayer = w.mLayer;
if (w.mBaseLayer == curBaseLayer || w.mIsImWindow || (i > 0 && w.mIsWallpaper)) {
curLayer += WINDOW_LAYER_MULTIPLIER;
} else {
curBaseLayer = curLayer = w.mBaseLayer;
}
// 更新该窗口的mAnimLayer，也就是动画显示时，该窗口的层级
assignAnimLayer(w, curLayer);
// TODO: Preserved old behavior of code here but not sure comparing
// oldLayer to mAnimLayer and mLayer makes sense...though the
// worst case would be unintentionalp layer reassignment.
if (w.mLayer != oldLayer || w.mWinAnimator.mAnimLayer != oldLayer) {
layerChanged = true;
anyLayerChanged = true;
}
// 将当前应用窗口的最高显示层级记录在mHighestApplicationLayer中
if (w.mAppToken != null) {
mHighestApplicationLayer = Math.max(mHighestApplicationLayer,
w.mWinAnimator.mAnimLayer);
}
// 对于分屏等相关的窗口，它们的显示层级需要再次处理
collectSpecialWindows(w);
if (layerChanged) {
w.scheduleAnimationIfDimming();
}
}
// 调整特殊窗口的层级
adjustSpecialWindows();
//TODO (multidisplay): Magnification is supported only for the default display.
if (mService.mAccessibilityController != null && anyLayerChanged
&& windows.get(windows.size() - 1).getDisplayId() == Display.DEFAULT_DISPLAY) {
mService.mAccessibilityController.onWindowLayersChangedLocked();
}
if (DEBUG_LAYERS) logDebugLayers(windows);
}
