1. Window和WindowManager

Window表示一個(gè)窗口的概念，如在創(chuàng)建對(duì)話(huà)框時(shí)就需要Window來(lái)進(jìn)行益楼。Window通過(guò)WindowManager來(lái)操作Window猾漫，但WIndow的具體實(shí)現(xiàn)都需要使用WindowManagerService

1.1 Window

1. WindowFlags

2. WindowType

• 應(yīng)用Window：對(duì)應(yīng)著一個(gè)Activity
• 子Window：不能單獨(dú)存在俊扭，需要附屬在特定的父Window上
• 系統(tǒng)Window：需要聲明權(quán)限才能創(chuàng)建的Window,例如Toast和系統(tǒng)狀態(tài)欄

如果采用TYPE_SYSTEM_ERROR队橙，需要聲明權(quán)限<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

3. Window分層

Z-index，應(yīng)用Window的層級(jí)范圍1-99萨惑，子Window范圍1000-1999捐康，系統(tǒng)Window層級(jí)范圍是2000-2999

4. WindowManager

• 增刪改Window實(shí)際上是操作Window里的View

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = new Button(this);
        btn.setText("TEST");
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT, 0, 0, PixelFormat.TRANSPARENT);
        params.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE| WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED;
        params.gravity = Gravity.LEFT| Gravity.TOP;
        params.x = 100;
        params.y = 300;
        params.type = WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG;
        getWindowManager().addView(btn, params);
    }
}

btn.setOnTouchListener(new View.OnTouchListener() {
                                   @Override
                                   public boolean onTouch(View view, MotionEvent motionEvent) {
                                       int rawX = (int) motionEvent.getX();
                                       int rawY = (int) motionEvent.getY();
                                       switch (motionEvent.getAction()) {
                                           case MotionEvent.ACTION_MOVE:
                                               params.x = rawX;
                                               params.y = rawY;
                                               mWindow.updateViewLayout(btn, params);
                                       }
                                       return false;
                                   }
                               }
        );

Window機(jī)制

2. Window的內(nèi)部機(jī)制

Window每一個(gè)都對(duì)應(yīng)著每一個(gè)View和每一個(gè)ViewRootImpl，因此Window不是實(shí)際存在的庸蔼，而是以View的形式存在的

2.1 Window的添加過(guò)程

@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);
}

WindowManagerGlobal的實(shí)現(xiàn)步驟：
步驟一：檢查參數(shù)是否合法解总，如果是子Window則需要調(diào)整一些參數(shù)

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;
// 如果是子View，則會(huì)調(diào)整參數(shù)
 if (parentWindow != null) {
     parentWindow.adjustLayoutParamsForSubWindow(wparams);
 }

步驟二：創(chuàng)建ViewRootImpl并將View添加到列表中
在WindowManagerGlobal內(nèi)部有如下幾個(gè)列表比較重要：

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>();

• mViews存儲(chǔ)的是所有Window所對(duì)應(yīng)的View姐仅，
• mRoots存儲(chǔ)的是所有Window所對(duì)應(yīng)的ViewRootImpl
• mParams存儲(chǔ)的是所有Window所對(duì)應(yīng)的布局參數(shù)
• mDyingViews則存儲(chǔ)了那些正在被刪除的View對(duì)象花枫，或者說(shuō)是那些已經(jīng)調(diào)用removeView方法但是刪除操作還未完成的Window對(duì)象。

在addView中通過(guò)如下方式將Window的一系列對(duì)象添加到列表中：

root = new ViewRootImpl(view.getContext(), display);

view.setLayoutParams(wparams);

mViews.add(view);
mRoots.add(root);
mParams.add(wparams);

步驟三：通過(guò)ViewRootImpl來(lái)更新界面并完成Window的添加過(guò)程

@Override
public void requestLayout() {
    if (!mHandlingLayoutInLayoutRequest) {
        checkThread();
        mLayoutRequested = true;
        scheduleTraversals();
    }
}

接著會(huì)通過(guò)mWindowSession最終來(lái)完成Window的添加過(guò)程掏膏。mWindowSession的類(lèi)型是IWindowSession劳翰，它是一個(gè)Binder對(duì)象，真正的實(shí)現(xiàn)類(lèi)是Session馒疹，也就是Window的添加過(guò)程是一次IPC調(diào)用佳簸。

在Session內(nèi)部會(huì)通過(guò)WindowManagerService來(lái)實(shí)現(xiàn)Window的添加

2.2 Window的刪除過(guò)程

WindowManagerGlobal#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); // 找到待刪除的View的Index
        View curView = mRoots.get(index).getView(); // 找到待刪除的View
        removeViewLocked(index, immediate); // 進(jìn)行刪除
        if (curView == view) {
            return;
        }

        throw new IllegalStateException("Calling with view " + view
                + " but the ViewAncestor is attached to " + curView);
    }
}

WindowManagerGlobal#removeViewLocked

private void removeViewLocked(int index, boolean immediate) {
     ViewRootImpl root = mRoots.get(index); // 從mRoots數(shù)組中找到對(duì)應(yīng)的root
     View view = root.getView(); // 找到對(duì)應(yīng)的View

     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);
         }
     }
 }

• removeViewLocked是通過(guò)ViewRootImpl來(lái)完成刪除操作的。在WindowManager中提供了兩種刪除接口removeView和removeViewImmediate颖变，它們分別表示異步刪除和同步刪除
• removeViewImmediate需要特別注意生均，一般來(lái)說(shuō)不需要使用此方法來(lái)刪除Window以免發(fā)生意外的錯(cuò)誤听想。這里主要說(shuō)異步刪除的情況，具體的刪除操作由ViewRootImpl的die方法來(lái)完成马胧。在異步刪除的情況下汉买，die方法只是發(fā)送了一個(gè)請(qǐng)求刪除的消息后就立刻返回了，這個(gè)時(shí)候View并沒(méi)有完成刪除操作佩脊，所以最后會(huì)將其添加到mDyingViews中录别，mDyingViews表示待刪除的View列表。ViewRootImpl的die方法如下所示：

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;
 }

同步刪除：doDie()方法邻吞，內(nèi)部會(huì)調(diào)用dispatchDetachedFromWindow方法
異步刪除：發(fā)送消息mHandler.sendEmptyMessage(MSG_DIE);
dispatchDetachedFromWindow方法：

• 垃圾回收相關(guān)工作，比如清楚數(shù)據(jù)和消息葫男、移除回調(diào)等
• 通過(guò)Session的remove方法刪除Window抱冷，最終會(huì)調(diào)用WindowManagerService的removeWindow方法
• 調(diào)用View的dispatchDetachedFromWindow
• 調(diào)用WindowManagerGlobal的doRemoveView方法刷新數(shù)據(jù)，包括mRoots梢褐，mParams以及mDyingViews旺遮，需要將當(dāng)前Window所關(guān)聯(lián)的這三類(lèi)對(duì)象從列表中刪除。
  

2.3 Window的更新過(guò)程

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);//替換掉老的LayoutParams

    synchronized (mLock) {
        int index = findViewLocked(view, true);
        ViewRootImpl root = mRoots.get(index);
        mParams.remove(index); //先刪除再增加
        mParams.add(index, wparams);
        root.setLayoutParams(wparams, false);
    }
}

首先它需要更新View的LayoutParams并替換掉老的LayoutParams盈咳，接著再更新ViewRootImpl中的LayoutParams耿眉，這一步是通過(guò)ViewRootImpl的setLayoutParams方法來(lái)實(shí)現(xiàn)的。在ViewRootImpl中會(huì)通過(guò)scheduleTraversals方法來(lái)對(duì)View重新布局鱼响，包括測(cè)量鸣剪，布局，重繪這三個(gè)過(guò)程丈积。除了View本身的重繪以外筐骇，ViewRootImpl還會(huì)通過(guò)WindowSession來(lái)更新Window的視圖，這個(gè)過(guò)程最終是由WindowManagerService的relayoutWindow()來(lái)具體實(shí)現(xiàn)的江滨，它同樣是一個(gè)IPC過(guò)程铛纬。

第八章(2)---Window的內(nèi)部機(jī)制

3. Window的創(chuàng)建過(guò)程

3.1 Activity的Window啟動(dòng)過(guò)程

3.2 Dialog的Window創(chuàng)建過(guò)程

3.3 Toast的Window創(chuàng)建過(guò)程

• TN是一個(gè)Binder類(lèi)，在NMS處理Toast請(qǐng)求時(shí)唬滑，需要Handler將其從Binder線(xiàn)程池中切換到發(fā)送Toast的線(xiàn)程告唆，因此Toast無(wú)法在沒(méi)有Looper的線(xiàn)程中彈出
• enqueueToast將Toast請(qǐng)求封裝成ToastRecord加入mToastQueue，mToastQueue最多存在50個(gè)彈出請(qǐng)求
• ToastRecord與NMS之間通過(guò)TN對(duì)象Callback的show,hide方法完成Toast的顯示和隱藏功能晶密，都是IPC