这里我们从一个悬浮窗应用来查看WindowManager的addView使用，从这里作为突破口来认识窗口的添加，和窗口的位置大小更新方法updateViewLayout，使用WindowManager的addView方法来添加窗口非常的直观，因为Activity的显示中，窗口的添加调用封装的太深了，

以下代码参考自https://blog.csdn.net/liufish992/article/details/122338344

private void initUi() {

DisplayMetrics metrics = getApplicationContext().getResources().getDisplayMetrics();

int width = metrics.widthPixels;

int height = metrics.heightPixels;

windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

LayoutInflater inflater = (LayoutInflater) getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);

floatView = (ViewGroup) inflater.inflate(R.layout.float_layout, null);

int layoutType;

layoutType = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;

WindowManager.LayoutParams floatLp = new WindowManager.LayoutParams(

(int) (width * (0.4f)),

(int) (height * (0.3f)),

layoutType,

WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,

PixelFormat.TRANSLUCENT

);

mLp = floatLp;

floatLp.gravity = Gravity.LEFT;//Gravity.CENTER;

floatLp.x = 0;

floatLp.y = 0;

windowManager.addView(floatView, floatLp);

位置变化设置

void move() {

mLp.x = 100;

mLp.y = 100;

windowManager.updateViewLayout(floatView, mLp);

}

使用dumpsys window windows查看

悬浮窗的信息，ty=APPLICATION_OVERLAY，appop=SYSTEM_ALERT_WINDOW

Window #8 Window{d3f21db u0 com.example.myapplication}:

mDisplayId=0 rootTaskId=1 mSession=Session{e489994 10075:u0a10159} mClient=android.os.BinderProxy@1cdc2d5

mOwnerUid=10159 showForAllUsers=false package=com.example.myapplication appop=SYSTEM_ALERT_WINDOW

mAttrs={(100,100)(432x646) gr=CENTER sim={adjust=pan} ty=APPLICATION_OVERLAY fmt=TRANSLUCENT

fl=NOT_FOCUSABLE HARDWARE_ACCELERATED

pfl=USE_BLAST INSET_PARENT_FRAME_BY_IME

bhv=DEFAULT

fitTypes=STATUS_BARS NAVIGATION_BARS CAPTION_BAR}

Requested w=432 h=646 mLayoutSeq=1429

mBaseLayer=111000 mSubLayer=0 mToken=WindowToken{bb70aea type=2038 android.os.BinderProxy@1cdc2d5}

Activity的信息，ty=BASE_APPLICATION

Window #11 Window{e656d83 u0 com.example.myapplication/com.example.myapplication.MainActivity}:

mDisplayId=0 rootTaskId=34 mSession=Session{e489994 10075:u0a10159} mClient=android.os.BinderProxy@3ae1c32

mOwnerUid=10159 showForAllUsers=false package=com.example.myapplication appop=NONE

mAttrs={(0,0)(fillxfill) sim={adjust=pan forwardNavigation} ty=BASE_APPLICATION wanim=0x10302fd

fl=LAYOUT_IN_SCREEN LAYOUT_INSET_DECOR SPLIT_TOUCH HARDWARE_ACCELERATED DRAWS_SYSTEM_BAR_BACKGROUNDS

pfl=NO_MOVE_ANIMATION FORCE_DRAW_STATUS_BAR_BACKGROUND USE_BLAST FIT_INSETS_CONTROLLED

bhv=DEFAULT

fitSides=}

Requested w=1080 h=2220 mLayoutSeq=1429

mBaseLayer=21000 mSubLayer=0 mToken=ActivityRecord{34f5722 u0 com.example.myapplication/.MainActivity} t34}

mActivityRecord=ActivityRecord{34f5722 u0 com.example.myapplication/.MainActivity} t34}

布局参数LayoutParams中最直观的就是窗口位置和大小，如果是全屏的，就不像是悬浮窗了。

Activity的显示中，也是会走到WindowManager的addView这里。

WindowManager的addView方法调用WindowManagerGlobal的addView，里面创建了ViewRootImpl对象，

注意这里布局参数LayoutParms的使用，ViewRootImpl在绘图时，使用了这个参数来构造悬浮窗。

修改窗口位置的调用updateViewLayout调用WindowManagerGlobal 对应的方法 updateViewLayout

// WindowManagerGlobal.java:

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 设置新的 LayoutParams

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 root.setLayoutParams(wparams, false) 方法，更新了 ViewRootImpl 的 LayoutParams

在 ViewRootImpl 的 setLayoutParams 方法中，会通过 scheduleTraversals 方法来对 View 重新布局和绘制，包括测量、布局、重绘这三个过程。

// ViewRootImpl.java:

void setLayoutParams(WindowManager.LayoutParams attrs, boolean newView) {

scheduleTraversals();

}

scheduleTraversals 调用PerformTraversals， 又调用relayoutWindow方法，

应用程序调用relayoutWindow来请求WMS为其创建一个Surface对象。frameworks\base\core\Java\android\view\ViewRootImpl.Java

private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility,

boolean insetsPending) throws RemoteException {

float appScale = mAttachInfo.mApplicationScale;

boolean restore = false;

if (params != null && mTranslator != null) {

restore = true;

params.backup();

mTranslator.translateWindowLayout(params);

}

if (params != null) {

if (DBG) Log.d(mTag, "WindowLayout in layoutWindow:" + params);

}

mPendingMergedConfiguration.getMergedConfiguration().seq = 0;

//Log.d(mTag, ">>>>>> CALLING relayout");

if (params != null && mOrigWindowType != params.type) {

// For compatibility with old apps, don't crash here.

if (mTargetSdkVersion < Build.VERSION_CODES.ICE_CREAM_SANDWICH) {

Slog.w(mTag, "Window type can not be changed after "

+ "the window is added; ignoring change of " + mView);

params.type = mOrigWindowType;

}

}

int relayoutResult = mWindowSession.relayout(

mWindow, mSeq, params,

(int) (mView.getMeasuredWidth() * appScale + 0.5f),

(int) (mView.getMeasuredHeight() * appScale + 0.5f),

viewVisibility, insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0,

mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets,

mPendingStableInsets, mPendingOutsets, mPendingBackDropFrame,

mPendingMergedConfiguration, mSurface);//这里传入变量mSurface

mPendingAlwaysConsumeNavBar =

(relayoutResult & WindowManagerGlobal.RELAYOUT_RES_CONSUME_ALWAYS_NAV_BAR) != 0;

//Log.d(mTag, "<<<<<< BACK FROM relayout");

if (restore) {

params.restore();

}

if (mTranslator != null) {

mTranslator.translateRectInScreenToAppWinFrame(mWinFrame);

mTranslator.translateRectInScreenToAppWindow(mPendingOverscanInsets);

mTranslator.translateRectInScreenToAppWindow(mPendingContentInsets);

mTranslator.translateRectInScreenToAppWindow(mPendingVisibleInsets);

mTranslator.translateRectInScreenToAppWindow(mPendingStableInsets);

}

return relayoutResult;

}

WMS服务在响应应用程序进程请求relayout调用时，首先在当前进程空间创建一个Surface对象，然后调用Session的relayout()函数进一步完成窗口布局过程，最后将WMS服务中创建的Surface返回给应用程序。

WMS中

frameworks\base\services\core\Java\com\android\server\wm\WindowManagerService.Java

同时，WMS的处理中也调用addWindow方法创建了对应的WindowState窗口对象。

猜想：在多窗口调用中，设置的ActivityOptions的bounds信息，在调用流程中，会传递给LayoutParams来控制窗口的位置和大小。

Intent it = new Intent(MainActivity.this, MainActivity2.class);

ActivityOptions ops = ActivityOptions.makeBasic();

ops.setLaunchBounds(new Rect(100, 100, 600, 700));

startActivity(it, ops.toBundle());

参考资料：

【Android】Window 机制_android window_一场雪ycx的博客-CSDN博客

https://blog.csdn.net/yangwen123/article/details/80674965?spm=1001.2014.3001.5502

https://blog.csdn.net/liufish992/article/details/122338344