public int type;

public int memoryType; // 保存窗口内存缓存类型

窗口内存缓存一共有4种,

public static final int MEMORY_TYPE_NORMAL = 0; //窗口缓冲位于主内存
public static final int MEMORY_TYPE_HARDWARE=1;//窗口缓冲位于可以被DMA访问,或者硬件加速的内存区域
public static final int MEMORY_TYPE_GPU = 2; //窗口缓冲位于可被图形加速器访问的区域
public static final int MEMORY_TYPE_PUSH_BUFFERS = 3; //窗口缓冲不拥有自己的缓冲区，不能被锁定，缓冲区由本地方法提供

2.3 窗口行为类型

public int flags; //保存窗口的行为

窗口行为类型的行为一共32种,数值都是2的n次幂,所以各种flags可以混合使用,直接按位或是最好的方法。

比如最开始四种行为定义如下,

//Flag：当该window对用户可见的时候，允许锁屏public static final int FLAG_ALLOW_LOCK_WHILE_SCREEN_ON     = 0x00000001;//Flag：让该window后所有的东西都成暗淡public static final int FLAG_DIM_BEHIND        = 0x00000002;//Flag：让该window后所有东西都模糊（4.0以上已经放弃这种毛玻璃效果）public static final int FLAG_BLUR_BEHIND        = 0x00000004;//Flag：让window不能获得焦点，这样用户快就不能向该window发送按键事public static final int FLAG_NOT_FOCUSABLE      = 0x00000008;

2.4 硬件加速类型

public int privateFlags;  // 保存硬件加速行为

一共有11种。定义如下,

public static final int PRIVATE_FLAG_FAKE_HARDWARE_ACCELERATED = 0x00000001;
public static final int PRIVATE_FLAG_FORCE_HARDWARE_ACCELERATED = 0x00000002;
public static final int PRIVATE_FLAG_WANTS_OFFSET_NOTIFICATIONS = 0x00000004;

2.5 窗口输入键盘类型

public int softInputMode;  

一共定义了13种键盘在窗口中的显示方法。

public static final int SOFT_INPUT_STATE_UNSPECIFIED = 0;
public static final int SOFT_INPUT_STATE_UNCHANGED = 1;

当然, WindowManager的一些其他变量也控制着窗口的显示形式。

3 应用窗口

3.1 一般应用窗口

ActivityThread的主线程ApplicationThread的performLaunchActivity方法会调用Activity的onCreate方法,在onCreate中会调用setContentView等方法加载解析xml资源。从Toast的最简单调用开始，它的调用代码是：

void makeVisible() {if (!mWindowAdded) {ViewManager wm = getWindowManager(); // 获取的是WindowManagerImpl对象wm.addView(mDecor, getWindow().getAttributes()); //  PhoneWindowmWindowAdded = true;}mDecor.setVisibility(View.VISIBLE);}

getAttributes最后获取的默认type类型是TYPE_APPLICATION。

3.2 Dialog

Dialog是一系列XXXDialog的基类，我们可以new任意Dialog或者通过Activity提供的 onCreateDialog(……)、onPrepareDialog(……)和showDialog(……)等方法来管理我们的Dialog，但是究 其实质都是来源于Dialog基类，所以我们对于各种XXXDialog来说只用分析Dialog的窗口加载就可以了。
Dialog构造方法如下,

Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {if (createContextThemeWrapper) {if (themeResId == 0) {final TypedValue outValue = new TypedValue();context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true);themeResId = outValue.resourceId;}mContext = new ContextThemeWrapper(context, themeResId);} else {mContext = context;
//mContext已经从外部传入的context对象获得值（一般是个Activity）！！！非常重要，先记住！！！}mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);final Window w = new PhoneWindow(mContext); // 创建新的WindowmWindow = w;w.setCallback(this);w.setOnWindowDismissedCallback(this);w.setWindowManager(mWindowManager, null, null);w.setGravity(Gravity.CENTER);mListenersHandler = new ListenersHandler(this);}

看看show方法,

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;}mCanceled = false;if (!mCreated) {dispatchOnCreate(null);}onStart();mDecor = mWindow.getDecorView();if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {final ApplicationInfo info = mContext.getApplicationInfo();mWindow.setDefaultIcon(info.icon);mWindow.setDefaultLogo(info.logo);mActionBar = new WindowDecorActionBar(this);}WindowManager.LayoutParams l = mWindow.getAttributes();//和上面分析的Activity一样type为TYPE_APPLICATIONif ((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;}try {mWindowManager.addView(mDecor, l);
//把一个View添加到Activity共用的windowManager里面去mShowing = true;sendShowMessage();} finally {}}

可以看见Dialog的新Window与Activity的Window的type同样都为TYPE_APPLICATION，上面介绍 WindowManager.LayoutParams时TYPE_APPLICATION的注释明确说过，普通应用程序窗口 TYPE_APPLICATION的token必须设置为Activity的token来指定窗口属于谁。所以可以看见，既然Dialog和 Activity共享同一个WindowManager（也就是上面分析的WindowManagerImpl），而WindowManagerImpl
里面有个Window类型的mParentWindow变量，这个变量在Activity的attach中创建WindowManagerImpl时传入 的为当前Activity的Window，而当前Activity的Window里面的mAppToken值又为当前Activity的token，所以 Activity与Dialog共享了同一个mAppToken值，只是Dialog和Activity的Window(PhoneWindow)对象不同。
为什么一定需要Activity的token 呢,禁止在当前activity中弹出另外一个activity的dialog,因为dialog有时候需要交互的,不能像toast一样(toast无交互).
所以传进去的context对象一定是Activity,如果是其他组件(Service)的context会报错。

4 子窗口

PopWindow是android系统中一个典型的子窗口,它的创建也依赖于Activity。
例如各种菜单(PopupMenu)都是利用PopWindow来实现的。
PopupWindow与Dialog一个不同点是PopupWindow是一个阻塞的对话框，如果你直接在Activity的onCreate等方法中显示它则会报错，所以PopupWindow最好另开启一个新线程去调用。
   PopupWindow一个构造函数如下,

public PopupWindow(View contentView, int width, int height, boolean focusable) {if (contentView != null) {mContext = contentView.getContext();//最终这个mContext实质是ActivitymWindowManager = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);}   // WindowManagersetContentView(contentView); // 初始化赋值setWidth(width);setHeight(height);setFocusable(focusable);}

显示时,最后都会调用showAsDropDown方法,

public void showAsDropDown(View anchor, int xoff, int yoff, int gravity) {if (isShowing() || mContentView == null) {return;}TransitionManager.endTransitions(mDecorView);registerForScrollChanged(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, gravity);updateAboveAnchor(aboveAnchor);invokePopup(p);}

createPopupLayoutParams方法会新建一个WindowManager.LayoutParams对象,然后变量type赋值为mWindowLayoutType,

private int mWindowLayoutType = WindowManager.LayoutParams.TYPE_APPLICATION_PANEL;

private void invokePopup(WindowManager.LayoutParams p) {if (mContext != null) {p.packageName = mContext.getPackageName();}final PopupDecorView decorView = mDecorView;decorView.setFitsSystemWindows(mLayoutInsetDecor);setLayoutDirectionFromAnchor();mWindowManager.addView(decorView, p);if (mEnterTransition != null) {decorView.requestEnterTransition(mEnterTransition);}}

PopWindow中没有像Activity及Dialog一样new新的Window, 完全使用了Activity的Window与WindowManager。

5 系统窗口

系统窗口的种类很多,以Toast为例来论述,
首先看Toast的构造方法,

public Toast(Context context) {mContext = context;mTN = new TN();mTN.mY = context.getResources().getDimensionPixelSize(com.android.internal.R.dimen.toast_y_offset);mTN.mGravity = context.getResources().getInteger(com.android.internal.R.integer.config_toastDefaultGravity);}

内部类TN构造方法如下,

TN() {// XXX This should be changed to use a Dialog, with a Theme.Toast// defined that sets up the layout params appropriately.final WindowManager.LayoutParams params = mParams;params.height = WindowManager.LayoutParams.WRAP_CONTENT;params.width = WindowManager.LayoutParams.WRAP_CONTENT;params.format = PixelFormat.TRANSLUCENT;params.windowAnimations = com.android.internal.R.style.Animation_Toast;params.type = WindowManager.LayoutParams.TYPE_TOAST;params.setTitle("Toast");params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;}

主要是为WindowManager.LayoutParams中的变量赋值, type赋值为

params.type = WindowManager.LayoutParams.TYPE_TOAST;

显示时,调用TN的handleShow方法,如下,

public void handleShow() {if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView+ " mNextView=" + mNextView);if (mView != mNextView) {// remove the old view if necessaryhandleHide();mView = mNextView;Context context = mView.getContext().getApplicationContext();String packageName = mView.getContext().getOpPackageName();if (context == null) {context = mView.getContext();}mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);// We can resolve the Gravity here by using the Locale for getting// the layout directionfinal Configuration config = mView.getContext().getResources().getConfiguration();final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());mParams.gravity = gravity;if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) {mParams.horizontalWeight = 1.0f;}if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) {mParams.verticalWeight = 1.0f;}mParams.x = mX;mParams.y = mY;mParams.verticalMargin = mVerticalMargin;mParams.horizontalMargin = mHorizontalMargin;mParams.packageName = packageName;if (mView.getParent() != null) {if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);mWM.removeView(mView);}if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this);mWM.addView(mView, mParams);trySendAccessibilityEvent();}}

和前2种窗口内型不同的是,系统窗口不依赖于Activity而存在,并且由系统服务统一管理,只是一个通知提示作用,并不会和Activity进行交互。
在使用Toast时context参数尽量使用getApplicationContext()，可以有效的防止静态引用导致的内存泄漏。

6 addView方法

mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);

通过这种方法获取的服务都是WindowManagerImpl对象,其addView方法如下,

public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {android.util.SeempLog.record_vg_layout(383,params);applyDefaultToken(params);mGlobal.addView(view, params, mDisplay, mParentWindow);}

直接调用WindowManagerGlobal的

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");}final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;if (parentWindow != null) {parentWindow.adjustLayoutParamsForSubWindow(wparams);} else {// If there's no parent, then hardware acceleration for this view is// set from the application's hardware acceleration setting.final Context context = view.getContext();if (context != null&& (context.getApplicationInfo().flags& ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;}}ViewRootImpl root;View panelParentView = null;synchronized (mLock) {// Start watching for system property changes.if (mSystemPropertyUpdater == null) {mSystemPropertyUpdater = new Runnable() {@Override public void run() {synchronized (mLock) {for (int i = mRoots.size() - 1; i >= 0; --i) {mRoots.get(i).loadSystemProperties();}}}};SystemProperties.addChangeCallback(mSystemPropertyUpdater);}int index = findViewLocked(view, false);if (index >= 0) {if (mDyingViews.contains(view)) {// Don't wait for MSG_DIE to make it's way through root's queue.mRoots.get(index).doDie();} else {throw new IllegalStateException("View " + view+ " has already been added to the window manager.");}// The previous removeView() had not completed executing. Now it has.}// If this is a panel window, then find the window it is being// attached to for future reference.if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {final int count = mViews.size();for (int i = 0; i < count; i++) {if (mRoots.get(i).mWindow.asBinder() == wparams.token) {panelParentView = mViews.get(i);}}}root = new ViewRootImpl(view.getContext(), display); // 初始化view.setLayoutParams(wparams);mViews.add(view);mRoots.add(root);mParams.add(wparams);}// do this last because it fires off messages to start doing thingstry {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;}}

最后的setView方法会调用performTraversals方法完成View的测量,确定位置以及显示,这样一个窗口就显示出来了。