一、window和windowmanager
window是一个抽象类，它的具体实现是phonewindow，创建一个window很简单，只需要创建一个windowmanager即可，window具体实现在windowmanagerservice中，windowmanager和windowmanagerservice的交互是一个ipc的过程。
下面是用windowmanager的例子:
我要评论
mfloatingbutton = new button(this);
mfloatingbutton.settext( "window");
mlayoutparams = new windowmanager.layoutparams(
layoutparams. wrap_content, layoutparams.wrap_content, 0, 0,
pixelformat. transparent);
mlayoutparams. flags = layoutparams.flag_not_touch_modal
| layoutparams. flag_not_focusable
| layoutparams. flag_show_when_locked;
mlayoutparams. type = layoutparams. type_system_error;
mlayoutparams. gravity = gravity. left | gravity. top;
mlayoutparams. x = 100;
mlayoutparams. y = 300;
mfloatingbutton.setontouchlistener( this);
mwindowmanager.addview( mfloatingbutton, mlayoutparams);
flags和type两个属性很重要，下面对一些属性进行介绍，首先是flags：
flag_not_touch_modal表示不需要获取焦点，也不需要接收各种输入，最终事件直接传递给下层具有焦点的window。
flag_not_focusable：在此window外的区域单击事件传递到底层window中。当前的区域则自己处理，这个一般都要设置，很重要。
flag_show_when_locked ：开启可以让window显示在锁屏界面上。
再来看下type这个参数：
window有三种类型：应用window，子window，系统window。应用类对应一个activity，子window不能单独存在，需要附属在父window上，比如常用的dialog。系统window是需要声明权限再创建的window，如toast等。
window有z-ordered属性，层级越大，越在顶层。应用window层级1-99，子window1000-1999，系统2000-2999。这此层级对应着windowmanager的type参数。系统层级常用的有两个type_system_overlay或者type_system_error。比如想用type_system_error，只需
mlayoutparams.type = layoutparams.type_system_error。还要添加权限<uses-permission andorid:name="android.permission.system_alert_window"/>。
有了对window的基本认识之后，我们来看下它底层如何实现加载view的。
二、window的创建
其实window的创建跟之前我写的一篇博客layoutinflater源码分析有点相似。window的创建是在activity创建的attach方法中，通过policymanager的makenewwindow方法。activity中实现了window的callback接口，因此当window状态改变时就会回调activity方法。如onattachedtowindow等。policymanager的真正实现类是policy，看下它的代码：
public window makenewwindow(context context) {
return new phonewindow(context);
}
到此window创建完成。
下面分析view是如何附属到window上的。看activity的setcontentview方法。
public void setcontentview(int layoutresid) {
getwindow().setcontentview(layoutresid);
initwindowdecoractionbar();
}
两部分，设置内容和设置actionbar。window的具体实现是phonewindow，看它的setcontent。
public void setcontentview(int layoutresid) {
// note: feature_content_transitions may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. do not check the feature
// before this happens.
if (mcontentparent == null) {
installdecor();
} else if (!hasfeature(feature_content_transitions)) {
mcontentparent.removeallviews();
}
if (hasfeature(feature_content_transitions)) {
final scene newscene = scene.getsceneforlayout(mcontentparent, layoutresid,
getcontext());
transitionto(newscene);
} else {
mlayoutinflater.inflate(layoutresid, mcontentparent);
}
final callback cb = getcallback();
if (cb != null && !isdestroyed()) {
cb.oncontentchanged();
}
}
看到了吧，又是分析它。
这里分三步执行：
1.如果没有decorview，在installdecor中的generatedecor()创建decorview。之前就分析过，这次就不再分析它了。
2.将view添加到decorview中的mcontentparent中。
3.回调activity的oncontentchanged接口。
经过以上操作，decorview创建了，但还没有正式添加到window中。在activityresumeactivity中首先会调用activity的onresume，再调用activity的makevisible，makevisible中真正添加view ，代码如下：
void makevisible() {
if (!mwindowadded) {
viewmanager wm = getwindowmanager();
wm.addview(mdecor, getwindow().getattributes());
mwindowadded = true;
}
mdecor.setvisibility(view.visible);
}
通过上面的addview方法将view添加到window。
三、window操作view内部机制
1.window的添加
一个window对应一个view和一个viewrootimpl,window和view通过viewrootimpl来建立联系，它并不存在，实体是view。只能通过 windowmanager来操作它。
windowmanager的实现类是windowmanagerimpl。它并没有直接实现三大操作，而是委托给windowmanagerglobal。addview的实现分为以下几步：
1）.检查参数是否合法。
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) {
parentwindow.adjustlayoutparamsforsubwindow(wparams);
} else {
// if there's no parent and we're running on l or above (or in the
// system context), assume we want hardware acceleration.
final context context = view.getcontext();
if (context != null
&& context.getapplicationinfo().targetsdkversion >= build.version_codes.lollipop) {
wparams.flags |= windowmanager.layoutparams.flag_hardware_accelerated;
}
}
2）.创建viewrootimpl并将view添加到列表中。
root = new viewrootimpl(view.getcontext(), display);
view.setlayoutparams(wparams);
mviews.add(view);
mroots.add(root);
mparams.add(wparams);
3）.通过viewrootimpl来更新界面并完成window的添加过程 。
root.setview(view, wparams, panelparentview);
上面的root就是viewrootimpl，setview中通过requestlayout()来完成异步刷新，看下requestlayout：
public void requestlayout() {
if (!mhandlinglayoutinlayoutrequest) {
checkthread();
mlayoutrequested = true;
scheduletraversals();
}
}
接下来通过windowsession来完成window添加过程，windowsession是一个binder对象，真正的实现类是 session，window的添加是一次ipc调用。
try {
morigwindowtype = mwindowattributes.type;
mattachinfo.mrecomputeglobalattributes = true;
collectviewattributes();
res = mwindowsession.addtodisplay(mwindow, mseq, mwindowattributes,
gethostvisibility(), mdisplay.getdisplayid(),
mattachinfo.mcontentinsets, mattachinfo.mstableinsets, 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);
}
在session内部会通过windowmanagerservice来实现window的添加。
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);
}
在windowmanagerservice内部会为每一个应用保留一个单独的session。
2.window的删除
看下windowmanagerglobal的removeview：
public void removeview(view view, boolean immediate) {
if (view == null) {
throw new illegalargumentexception("view must not be null");
}
synchronized (mlock) {
int index = findviewlocked(view, true);
view curview = mroots.get(index).getview();
removeviewlocked(index, immediate);
if (curview == view) {
return;
}
throw new illegalstateexception("calling with view " + view
+ " but the viewancestor is attached to " + curview);
}
}
首先调用findviewlocked来查找删除view的索引，这个过程就是建立数组遍历。然后再调用removeviewlocked来做进一步的删除。
private void removeviewlocked(int index, boolean immediate) {
viewrootimpl root = mroots.get(index);
view view = root.getview();
if (view != null) {
inputmethodmanager imm = inputmethodmanager.getinstance();
if (imm != null) {
imm.windowdismissed(mviews.get(index).getwindowtoken());
}
}
boolean deferred = root.die(immediate);
if (view != null) {
view.assignparent(null);
if (deferred) {
mdyingviews.add(view);
}
}
}
真正删除操作是viewrootimpl来完成的。windowmanager提供了两种删除接口，removeviewimmediate，removeview。它们分别表示异步删除和同步删除。具体的删除操作由viewrootimpl的die来完成。
boolean die(boolean immediate) {
// make sure we do execute immediately if we are in the middle of a traversal or the damage
// done by dispatchdetachedfromwindow will cause havoc on return.
if (immediate && !misintraversal) {
dodie();
return false;
}
if (!misdrawing) {
destroyhardwarerenderer();
} else {
log.e(tag, "attempting to destroy the window while drawing!\n" +
" window=" + this + ", title=" + mwindowattributes.gettitle());
}
mhandler.sendemptymessage(msg_die);
return true;
}
由上可知如果是removeviewimmediate，立即调用dodie，如果是removeview，用handler发送消息，viewrootimpl中的handler会处理消息并调用dodie。重点看下dodie:
void dodie() {
checkthread();
if (local_logv) log.v(tag, "die in " + this + " of " + msurface);
synchronized (this) {
if (mremoved) {
return;
}
mremoved = true;
if (madded) {
dispatchdetachedfromwindow();
}
if (madded && !mfirst) {
destroyhardwarerenderer();
if (mview != null) {
int viewvisibility = mview.getvisibility();
boolean viewvisibilitychanged = mviewvisibility != viewvisibility;
if (mwindowattributeschanged || viewvisibilitychanged) {
// if layout params have been changed, first give them
// to the window manager to make sure it has the correct
// animation info.
try {
if ((relayoutwindow(mwindowattributes, viewvisibility, false)
& windowmanagerglobal.relayout_res_first_time) != 0) {
mwindowsession.finishdrawing(mwindow);
}
} catch (remoteexception e) {
}
}
msurface.release();
}
}
madded = false;
}
windowmanagerglobal.getinstance().doremoveview(this);
}
主要做四件事:
1.垃圾回收相关工作，比如清数据，回调等。
2.通过session的remove方法删除window,最终调用windowmanagerservice的removewindow
3.调用dispathdetachedfromwindow，在内部会调用ondetachedfromwindow()和ondetachedfromwindowinternal()。当view移除时会调用ondetachedfromwindow，它用于作一些资源回收。
4.通过doremoveview刷新数据，删除相关数据，如在mroot，mdyingviews中删除对象等。
void doremoveview(viewrootimpl root) {
synchronized (mlock) {
final int index = mroots.indexof(root);
if (index >= 0) {
mroots.remove(index);
mparams.remove(index);
final view view = mviews.remove(index);
mdyingviews.remove(view);
}
}
if (hardwarerenderer.strimforeground && hardwarerenderer.isavailable()) {
dotrimforeground();
}
}
3.更新window
看下windowmanagerglobal中的updateviewlayout。
public void updateviewlayout(view view, viewgroup.layoutparams params) {
if (view == null) {
throw new illegalargumentexception("view must not be null");
}
if (!(params instanceof windowmanager.layoutparams)) {
throw new illegalargumentexception("params must be windowmanager.layoutparams");
}
final windowmanager.layoutparams wparams = (windowmanager.layoutparams)params;
view.setlayoutparams(wparams);
synchronized (mlock) {
int index = findviewlocked(view, true);
viewrootimpl root = mroots.get(index);
mparams.remove(index);
mparams.add(index, wparams);
root.setlayoutparams(wparams, false);
}
}
通过viewrootimpl的setlayoutparams更新viewrootimpl的layoutparams,接着scheduletraversals对view重新布局，包括测量，布局，重绘，此外它还会通过windowsession来更新window。这个过程由windowmanagerservice实现。这跟上面类似，就不再重复，到此window底层源码就分析完啦。
以上就是本文的全部内容,希望对大家的学习有所帮助。
如对本文有疑问， 点击进行留言回复！！
LongClick原理、上下文菜单原理、EditText长按弹窗原理、WebView长按弹窗自定义、修复WebView全选重复bug ———————————————— 版权声明：本文为CSDN博主「
JobScheduler 实现 特定时间，特定条件（系统空闲，电池电量，磁盘空间 ……）下执行任务
网友评论