正文
android window(二)从getSystemService到WindowManagerGlobal
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在Activity调用getSystemService(WINDOW_SERVICE) 调用的是父类ContextThemeWrapper
package android.view;
public class ContextThemeWrapper extends ContextWrapper {
@Override
public Object getSystemService(String name) {
if (LAYOUT_INFLATER_SERVICE.equals(name)) {
if (mInflater == null) {
mInflater = LayoutInflater.from(getBaseContext()).cloneInContext(this);
}
return mInflater;
}
return getBaseContext().getSystemService(name);
}
}
这里getBaseContext返回是context的实现类ContextImpl
//ContextImpl
@Override
public Object getSystemService(String name) {
return SystemServiceRegistry.getSystemService(this, name);
}//SystemServiceRegistry
public static Object getSystemService(ContextImpl ctx, String name) {
ServiceFetcher<?> fetcher = SYSTEM_SERVICE_FETCHERS.get(name);
return fetcher != null ? fetcher.getService(ctx) : null;
}
SYSTEM_SERVICE_FETCHERS是一个map，key为WINDOW_SERVICE时，对应的value是什么？
ContextImpl.java 的源码
208 class ContextImpl extends Context {
//...
628 registerService(WINDOW_SERVICE, new ServiceFetcher() {
629 Display mDefaultDisplay;
630 public Object getService(ContextImpl ctx) {
631 Display display = ctx.mDisplay;
632 if (display == null) {
633 if (mDefaultDisplay == null) {
634 DisplayManager dm = (DisplayManager)ctx.getOuterContext().
635 getSystemService(Context.DISPLAY_SERVICE);
636 mDefaultDisplay = dm.getDisplay(Display.DEFAULT_DISPLAY);
637 }
638 display = mDefaultDisplay;
639 }
640 return new WindowManagerImpl(display);
641 }});1829 @Override
1830 public Object getSystemService(String name) {
1831 ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);
1832 return fetcher == null ? null : fetcher.getService(this);
1833 }
//...
}
WindowManagerImpl.java
public final class WindowManagerImpl implements WindowManager {
private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
private final Display mDisplay;
private final Window mParentWindow;
//...
public WindowManagerImpl createLocalWindowManager(Window parentWindow) {
return new WindowManagerImpl(mDisplay, parentWindow);
} public WindowManagerImpl createPresentationWindowManager(Display display) {
return new WindowManagerImpl(display, mParentWindow);
} @Override
public void addView(View view, ViewGroup.LayoutParams params) {
mGlobal.addView(view, params, mDisplay, mParentWindow);
} @Override
public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
mGlobal.updateViewLayout(view, params);
} @Override
public void removeView(View view) {
mGlobal.removeView(view, false);
} @Override
public void removeViewImmediate(View view) {
mGlobal.removeView(view, true);
} @Override
public Display getDefaultDisplay() {
return mDisplay;
}
}
WindowManager.java
public interface WindowManager extends ViewManager {
//...
}
ViewManager.java
public interface ViewManager
{
public void addView(View view, ViewGroup.LayoutParams params);
public void updateViewLayout(View view, ViewGroup.LayoutParams params);
public void removeView(View view);
}
WindowManager的addView的过程，WindowManager是个接口，它的实现类是WindowManagerImpl类，而WindowManagerImpl又把相关逻辑交给了WindowManagerGlobal处理。WindowManagerGlobal是个单例类，它在进程中只存在一个实例，是它内部的addView方法最终创建了我们的核心类ViewRootImpl。
可以看到这里的WindowManagerImpl 的主要功能都是通过WindowManagerGlobal来实现的
WindowManagerGlobal.java
public final class WindowManagerGlobal {
private static final String TAG = "WindowManager"; //...
private static WindowManagerGlobal sDefaultWindowManager;
private static IWindowManager sWindowManagerService;
private static IWindowSession sWindowSession; private final Object mLock = new Object(); private final ArrayList<View> mViews = new ArrayList<View>();
private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();
private final ArrayList<WindowManager.LayoutParams> mParams =
new ArrayList<WindowManager.LayoutParams>();
private final ArraySet<View> mDyingViews = new ArraySet<View>(); private Runnable mSystemPropertyUpdater; private WindowManagerGlobal() {
} public static WindowManagerGlobal getInstance() {
synchronized (WindowManagerGlobal.class) {
if (sDefaultWindowManager == null) {
sDefaultWindowManager = new WindowManagerGlobal();
}
return sDefaultWindowManager;
}
} public static IWindowManager getWindowManagerService() {
synchronized (WindowManagerGlobal.class) {
if (sWindowManagerService == null) {
sWindowManagerService = IWindowManager.Stub.asInterface(
ServiceManager.getService("window"));
}
return sWindowManagerService;
}
} public static IWindowSession getWindowSession() {
synchronized (WindowManagerGlobal.class) {
if (sWindowSession == null) {
try {
InputMethodManager imm = InputMethodManager.getInstance();
IWindowManager windowManager = getWindowManagerService();
sWindowSession = windowManager.openSession(
new IWindowSessionCallback.Stub() {
@Override
public void onAnimatorScaleChanged(float scale) {
ValueAnimator.setDurationScale(scale);
}
},
imm.getClient(), imm.getInputContext());
ValueAnimator.setDurationScale(windowManager.getCurrentAnimatorScale());
} catch (RemoteException e) {
Log.e(TAG, "Failed to open window session", e);
}
}
return sWindowSession;
}
} public static IWindowSession peekWindowSession() {
synchronized (WindowManagerGlobal.class) {
return sWindowSession;
}
} public String[] getViewRootNames() {
synchronized (mLock) {
final int numRoots = mRoots.size();
String[] mViewRoots = new String[numRoots];
for (int i = 0; i < numRoots; ++i) {
mViewRoots[i] = getWindowName(mRoots.get(i));
}
return mViewRoots;
}
} public View getRootView(String name) {
synchronized (mLock) {
for (int i = mRoots.size() - 1; i >= 0; --i) {
final ViewRootImpl root = mRoots.get(i);
if (name.equals(getWindowName(root))) return root.getView();
}
} return null;
} public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
//...
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.
synchronized (mLock) {
final int index = findViewLocked(view, false);
if (index >= 0) {
removeViewLocked(index, true);
}
}
throw e;
}
} 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);
}
} 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);
}
} public void closeAll(IBinder token, String who, String what) {
//...
} 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);
}
}
} 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();
}
} private int findViewLocked(View view, boolean required) {
final int index = mViews.indexOf(view);
if (required && index < 0) {
throw new IllegalArgumentException("View=" + view + " not attached to window manager");
}
return index;
} //...
}
每个应用进程，仅有一个 sWindowSession 对象，它对应了 WmS 中的 Session 子类，WmS 为每一个应用进程分配一个 Session 对象。WindowState 类有一个 IWindow mClient 参数，是由 Session 调用 addToDisplay 传递过来的，对应了 ViewRootImpl 中的 W 类的实例。
WindowManagerGlobal的addView里面初始化了
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
//...
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.
synchronized (mLock) {
final int index = findViewLocked(view, false);
if (index >= 0) {
removeViewLocked(index, true);
}
}
throw e;
}
}
WindowManagerGlobal的窗口管理:
WindowManager的总结
经过前文的分析，相信读者对WindowManager的工作原理有了深入的认识。
鉴于窗口布局和控件布局的一致性，WindowManager继承并实现了接口ViewManager。
使用者可以通过Context.getSystemService(Context.WINDOW_SERVICE)来获取一个WindowManager的实例。这个实例的真实类型是WindowManagerImpl。WindowManagerImpl一旦被创建就确定了通过它所创建的窗口所属哪块屏幕？哪个父窗口？
WindowManagerImpl除了保存了窗口所属的屏幕以及父窗口以外，没有任何实质性的工作。窗口的管理都交由WindowManagerGlobal的实例完成。
WindowManagerGlobal在一个进程中只有一个实例。
WindowManagerGlobal在3个数组中统一管理整个进程中的所有窗口的信息。这些信息包括控件、布局参数以及ViewRootImpl三个元素。
除了管理窗口的上述3个元素以外，WindowManagerGlobal将窗口的创建、销毁与布局更新等任务交付给了ViewRootImpl完成。
说明 在实际的应用开发过程中，有时会在logcat的输出中遇到有关WindowLeaked的异常输出。WindowLeaked异常发生与WindowManagerGlobal中，其原因是Activity在destroy之前没有销毁其附属窗口，如对话框、弹出菜单等。
如此看来，WindowManager的实现仍然是很轻量的。窗口的创建、销毁与布局更新都指向了一个组件：ViewRootImpl。
