最近工作中总会涉及到Insets相关的一些内容，网上对于Insets的分析以及介绍还是较少的，这里对Insets涉及到一些概念和方法做一个总结。

什么是Insets？

WindowInsets 源码解释为 window content的一系列插值集合，（个人理解为 一个Activity相对于手机屏幕需要空出的地方以腾纳给statusbar、Ime、Navigationbar等系统窗口，具体表现为该区域需要的上下左右的宽高，比如输入法窗口的区域就是一个Inset）

WindowInsets包括三类：SystemWindowInsets、StableInsets、WIndowDecorInsets

• SystemWindowInsets：全窗口下，被navigationbar、statusbar、ime或其他系统窗口覆盖的区域
• StableInsets：全窗口下，被系统UI覆盖的区域
• WIndowDecorInsets：系统预留属性

Insets相关类

InsetsState

保存系统中所有的Insets的状态，他是状态描述者，持有系统中可以产生Window Insets的window状态 private InsetsSource[] mSources = new InsetsSource[SIZE]; // mSources变量维护所有产生Insets的window（也就是InsetsSource）的状态

它主要持有以下几种类型的Insets

ITYPE_STATUS_BAR,
ITYPE_NAVIGATION_BAR,
ITYPE_CAPTION_BAR,
ITYPE_TOP_GESTURES,
ITYPE_BOTTOM_GESTURES,
ITYPE_LEFT_GESTURES,
ITYPE_RIGHT_GESTURES,
ITYPE_TOP_TAPPABLE_ELEMENT,
ITYPE_BOTTOM_TAPPABLE_ELEMENT,
ITYPE_LEFT_DISPLAY_CUTOUT,
ITYPE_TOP_DISPLAY_CUTOUT,
ITYPE_RIGHT_DISPLAY_CUTOUT,
ITYPE_BOTTOM_DISPLAY_CUTOUT,
ITYPE_IME,
ITYPE_CLIMATE_BAR,
ITYPE_EXTRA_NAVIGATION_BAR

如果InsetsState发生改变后，会通过MSG_INSETS_CHANGED消息发送到InsetsController，进行修改并保存到变量mState中

public boolean onStateChanged(InsetsState state) {
    boolean stateChanged = !mState.equals(state, true /* excludingCaptionInsets */,false /* excludeInvisibleIme */) || !captionInsetsUnchanged();
    if (!stateChanged && mLastDispatchedState.equals(state)) {
        return false;
    }
    updateState(state);

    boolean localStateChanged = !mState.equals(mLastDispatchedState,
            true /* excludingCaptionInsets */, true /* excludeInvisibleIme */);
    mLastDispatchedState.set(state, true /* copySources */);

    applyLocalVisibilityOverride();
    if (localStateChanged) {
        if (DEBUG) Log.d(TAG, "onStateChanged, notifyInsetsChanged, send state to WM: " + mState);
        mHost.notifyInsetsChanged();
        updateRequestedState();
    }
    return true;
}

InsetsState的关键方法：

WindowInsets calculateInsets（...）：基于当前source设置计算新的windowInsets
void processSource（InsetsSource source，...）:  根据计算值更新source值

InsetsStateController

管理所有窗口的Insets的state

private final InsetsState mLastState = new InsetsState();  //旧的InsetsState
private final InsetsState mState = new InsetsState();  //新的InsetsState

几个重要的方法：

private boolean isAboveIme(WindowContainer target）// 判断当前窗口是否处在输入法窗口层级上
void onImeControlTargetChanged(@Nullable InsetsControlTarget imeTarget) //当输入法target 窗口发生变化触发
InsetsState getInsetsForDispatch(@NonNull WindowState target)  //分发Insets 对Insets进一步更新（更新frame 或者visible）

InsetsSource

是Insets产生者的描述，记录每一个产生Insets的window的状态，主要记录产生的Insets区域

private final @InternalInsetsType int mType;    //Insets类型  nav或者status或者...
private final Rect mFrame;    //代表Insets区域
private boolean mVisible;     //Insets可见性

/*几个重要的方法/

public void setFrame(Rect frame)   //设置Insets大小
public void setVisible(boolean visible)  //设置Insets可见性
private Insets calculateInsets(Rect relativeFrame, Rect frame, boolean ignoreVisibility)   //根据frame以及ignoreVisibility  计算Insets

InsetsSourceConsumer（ImeInsetsSourceConsumer）

对单一InsetsSource的消费者，其内部持有InsetsSourceControl，可以控制其leash的可见性和动画，输入法有专门的ImeInsetsSourceConsumer来消费输入法的Insets

protected boolean mRequestedVisible;   //单一Insets的可见性
private @Nullable InsetsSourceControl mSourceControl;  // 持有InsetsSourceControl变量可以实现对单一InsetsSource的控制
protected final InsetsController mController; //所属的InsetController
protected final InsetsState mState;   //本地state

/几个重要的方法/

public void updateSource(InsetsSource newSource, @AnimationType int animationType)   //更新mstate中的source 主要更新frame
public void show(boolean fromIme) //显示Insets
protected void setRequestedVisible(boolean requestedVisible)  //设置Insets的可见性
public void setControl(@Nullable InsetsSourceControl control,
        @InsetsType int[] showTypes, @InsetsType int[] hideTypes) //后面讲
public void hide()  //隐藏Insets
boolean applyLocalVisibilityOverride()  //主要更新state可见性
protected boolean isRequestedVisibleAwaitingControl() //判断当前Insets是否会在获得control时更新可见性，即判断是否存在pending show（如果是bars 该方法等同于isRequestedVisible）

ImeInsetsSourceConsumer

private boolean mIsRequestedVisibleAwaitingControl;   //判断是否存在一个请求要让输入法显示出来（但是由于当前尚未获得control因此暂时无法实现这个操作）
void notifyHidden()   //控制IMM隐藏输入法
public @ShowResult int requestShow(boolean fromIme) //控制IMM显示输入法
public void removeSurface()  //移除输入法的surface
- InsetsSourceControl
对InsetsSource的控制者，用来控制Insets的产生者，内部持有控制输入法动画的Leash
private final @InternalInsetsType int mType;    //InsetsSource类型
private final @Nullable SurfaceControl mLeash;    //播放动画需要的Leash ，app可以控制对其设置position实现位移动画
private final Point mSurfacePosition;    //当前leash(Surface)在屏幕中的position
- InsetsSourceProvider
他是特定InsetsSource在server端的控制者，他被称作provider是因为他提供InsetsSource给客户端（客户端通过InsetsSourceConsumer使用InsetsSource）

这里重点关注ImeInsetsSourceProvider

private InsetsControlTarget mImeTargetFromIme;   //输入法Insets的control（Insets需要有一个control，否则他就会失控 不可控制）
private Runnable mShowImeRunner;   //显示输入法线程
private boolean mIsImeLayoutDrawn;  //输入法是否已经绘制完成

void scheduleShowImePostLayout(InsetsControlTarget imeTarget) //开始显示输入法 创建输入法显示线程
void checkShowImePostLayout()  //判断当前是否满足显示输入法条件若是则run输入法显示线程
boolean isImeTargetFromDisplayContentAndImeSame()  //判断输入法目标窗口是否满足显示输入法的条件（包括判断是否在closing、是否一致等等） S的代码会比较简约 R的代码有点复杂冗余

InsetsController

它是WindowInsets在client端的实现 用来控制insets ，InsetsController只在ViewRootImpl里面创建的，每个Window会对应一个ViewRootImpl，同样每个ViewRootImpl会对应每个InsetsController

/*关键成员变量*/
InsetsState mState = new InsetsState();   //记录本地State （Client端的Insetsstate）
InsetsState mLastDispatchedState = new InsetsState(); //从system端传来的InsetsState
InsetsState mRequestedState = new InsetsState(); //发送给系统端的InsetsState
SparseArray<InsetsSourceConsumer> mSourceConsumers = new SparseArray<>(); //持有sourceConsumers

/*关键方法*/
public void applyImeVisibility(boolean setVisible) //更新输入法可见性
public void notifyFinished(InsetsAnimationControlRunner runner, boolean shown) //动画结束时回调方法
public void onControlsChanged(InsetsSourceControl[] activeControls) //当系统端分发新的Insets Controls时被调用
public boolean onStateChanged(InsetsState state) //Insets或者InsetsControl发生改变会调用
public void setSystemBarsBehavior(@Behavior int behavior)
public void setSystemBarsAppearance(@Appearance int appearance, @Appearance int mask)   //更改Systembar的表现行为
public void show(@InsetsType int types, boolean fromIme) //显示Insets
void hide(@InsetsType int types, boolean fromIme)   //隐藏Insets
private void updateState(InsetsState newState)  //更新state
private void updateRequestedState()  //如果Insets在client端发生改变再重新发送到server端
public void applyAnimation(@InsetsType final int types, boolean show, boolean fromIme)    //更新Insets动画

InsetsChanged、InsetsControlChanged方法

Insets的变化一般是通过消息机制来进行更改的，主要是两方面的更改包括InsetsChanged和InsetsControlChanged，他们是由System_server经过WindowState调用到App进程的。

WindowState.java  //属于Server端
void notifyInsetsChanged() {
    ProtoLog.d(WM_DEBUG_IME, "notifyInsetsChanged for %s ", this);
    try {
        mClient.insetsChanged(getInsetsState());
    } catch (RemoteException e) {
        Slog.w(TAG, "Failed to deliver inset state change w=" + this, e);
    }
}

ViewRootImpl#W
@Override
public void insetsChanged(InsetsState insetsState) {
    final ViewRootImpl viewAncestor = mViewAncestor.get();
    if (viewAncestor != null) {
        viewAncestor.dispatchInsetsChanged(insetsState);
    }
}

@Override
public void insetsControlChanged(InsetsState insetsState,
        InsetsSourceControl[] activeControls) {
    final ViewRootImpl viewAncestor = mViewAncestor.get();
    if (viewAncestor != null) {
        viewAncestor.dispatchInsetsControlChanged(insetsState, activeControls);
    }
}

异步发送消息：MSG_INSETS_CHANGED、MSG_INSETS_CONTROL_CHANGED

case MSG_INSETS_CHANGED:
    mInsetsController.onStateChanged((InsetsState) msg.obj);
    break;
case MSG_INSETS_CONTROL_CHANGED: {
    mInsetsController.onStateChanged((InsetsState) args.arg1);
    mInsetsController.onControlsChanged((InsetsSourceControl[]) args.arg2);
    break;   //首先都会调用InsetsController的onStateChanged方法
}

onStateChanged

public boolean onStateChanged(InsetsState state) {
    boolean stateChanged = !mState.equals(state, true /* excludingCaptionInsets */,false /* excludeInvisibleIme */)  //判断client端state和传来的state是否一致
            || !captionInsetsUnchanged();
    //同时判断上次server端传来的state是否同当前传传来的state一致
    if (!stateChanged && mLastDispatchedState.equals(state)) {
        return false;
    }
    if (DEBUG) Log.d(TAG, "onStateChanged: " + state);
    updateState(state); 
    //判断client端本地state是否已经发生改变
    boolean localStateChanged = !mState.equals(mLastDispatchedState,
            true /* excludingCaptionInsets */, true /* excludeInvisibleIme */);
    //更新mLastDispatchedState  即更新server端传来的state
    mLastDispatchedState.set(state, true /* copySources */);
    //将更新apply到本地
    applyLocalVisibilityOverride();
    if (localStateChanged) {
        if (DEBUG) Log.d(TAG, "onStateChanged, notifyInsetsChanged, send state to WM: " + mState);
        //如果本地Insets发生改变了，通知server端Insets更改了
        mHost.notifyInsetsChanged();
        //更新传递给server端的InsetsState
        updateRequestedState();
    }
    return true;
}

onControlsChanged

该方法在窗口获取焦点或者失去焦点的时候也会调用到

public void onControlsChanged(InsetsSourceControl[] activeControls) {
    if (activeControls != null) {
        for (InsetsSourceControl activeControl : activeControls) {
            if (activeControl != null) {
                // TODO(b/122982984): Figure out why it can be null.
                mTmpControlArray.put(activeControl.getType(), activeControl);
            }
        }
    }

    boolean requestedStateStale = false;
    final int[] showTypes = new int[1]; //系统Insets会根据showTypes数组内的值去更新可见性
    final int[] hideTypes = new int[1];

   //遍历所有的SourceConsumer  更新system_server传来的InsetsSourceControl
    for (int i = mSourceConsumers.size() - 1; i >= 0; i--) {
        final InsetsSourceConsumer consumer = mSourceConsumers.valueAt(i);
        final InsetsSourceControl control = mTmpControlArray.get(consumer.getType());
        consumer.setControl(control, showTypes, hideTypes);
    }

    // Ensure to create source consumers if not available yet.
    //便利system_server传递来的InsetsSourceControl
    for (int i = mTmpControlArray.size() - 1; i >= 0; i--) {
        final InsetsSourceControl control = mTmpControlArray.valueAt(i);
        final @InternalInsetsType int type = control.getType();
        final InsetsSourceConsumer consumer = getSourceConsumer(type);
//如果consumer不存在会创建
        consumer.setControl(control, showTypes, hideTypes); //可以看到如果存在対赢得consumer  会调用setControl方法两次

     ...

    }
    mTmpControlArray.clear();
    
    //showTypes、hideTypes值会在setControl方法内进行修改
    int animatingTypes = invokeControllableInsetsChangedListeners();
    showTypes[0] &= ~animatingTypes;
    hideTypes[0] &= ~animatingTypes;

    //假设showTypes[0]=8 代表要显示输入法
    if (showTypes[0] != 0) {
        applyAnimation(showTypes[0], true /* show */, false /* fromIme */);
    }
    //假设hideTypes[0]=8 代表要隐藏输入法
    if (hideTypes[0] != 0) {
        applyAnimation(hideTypes[0], false /* show */, false /* fromIme */);
    }
    if (requestedStateStale) {
        updateRequestedState();
    }
}

总结

1. 每个ViewRootImpl对应一个InsetsController实例，他是一个App进程中控制Insets的核心类，用于保存传递系统中产生Insets的window的状态和动画需要的leash以及控制播放动画
2. InsetsSource是对产生Insets的窗口的状态描述，包括可见性以及Insets的大小
3. 每个InsetsController会持有一个成员变量mState（InsetsState），它保存了系统中所有产生Insets的Window（InsetsSource）的状态列表，状态主要是指可见性以及产生Insets的window的区域大小
4. InsetsSourceConsumer 是用来消费特定InsetsSource，消费主要是指对产生Insets 的window即InsetsSource进行可见性控制以及播放动画，通过持有的window的Leash来实现，也就是mSourceControl（InsetsSourceControl）
5. 每个InsetsController会持有多个InsetsSourceConsumer，他持有一个InsetsSourceConsumers列表，SparseArray mSourceConsumers

到这里Insets已经总结完毕，后续将进一步通过源码分析Insets的原理以及和App之间的关系，由于水平有限，难免有错误，若在阅读时发现不妥或者错误的地方留言指正，共同进步，谢谢!

Have a nice day!