Android应用程序键盘（Keyboard）消息处理机制分析（10）

Step 2. ViewRoot.requestLayout

这个函数定义在frameworks/base/core/java/android/view/ViewRoot.java文件中：

public final class ViewRoot extends Handler implements ViewParent,
        View.AttachInfo.Callbacks {
    ......

    public void requestLayout() {
        ......
        mLayoutRequested = true;
        scheduleTraversals();
    }

    ......
}

         这个函数调用了scheduleTraversals函数来进一步执行操作，由于篇幅关系，我们就不详细描述scheduleTraversals函数了，简单来说，在scheduleTraversals函数中，会通过sendEmptyMessage(DO_TRAVERSAL)发送一个消息到应用程序的消息队列中，这个消息最终由ViewRoot的handleMessage函数处理，而ViewRoot的handleMessage函数把这个消息交给ViewRoot类的performTraversals来处理，在performTraversals函数中，又会调用ViewRoot类的relayoutWindow函数来进一步执行操作，最后在relayoutWindow函数中，就会通过WindowManagerService内部类Session的远程接口sWindowSession的relayout函数来进入到WindowManagerService中。

 

        Step 3. WindowManagerService.Session.relayout

        这个函数定义在frameworks/base/services/java/com/android/server/WindowManagerService.java 文件中：

public class WindowManagerService extends IWindowManager.Stub
        implements Watchdog.Monitor {
    ......

    private final class Session extends IWindowSession.Stub
            implements IBinder.DeathRecipient {
        ......

        public int relayout(IWindow window, WindowManager.LayoutParams attrs,
                int requestedWidth, int requestedHeight, int viewFlags,
                boolean insetsPending, Rect outFrame, Rect outContentInsets,
                Rect outVisibleInsets, Configuration outConfig, Surface outSurface) {
            //Log.d(TAG, ">>>>>> ENTERED relayout from " + Binder.getCallingPid());
            int res = relayoutWindow(this, window, attrs,
                    requestedWidth, requestedHeight, viewFlags, insetsPending,
                    outFrame, outContentInsets, outVisibleInsets, outConfig, outSurface);
            //Log.d(TAG, "<<<<<< EXITING relayout to " + Binder.getCallingPid());
            return res;
        }

        ......
    }

    ......
}

 

        这个函数只是简单地调用WindowManagerService的成员函数relayoutWIndow来进一步处理。

        Step 4. WindowManagerService.relayoutWIndow

        这个函数定义在frameworks/base/services/java/com/android/server/WindowManagerService.java 文件中：

public class WindowManagerService extends IWindowManager.Stub
        implements Watchdog.Monitor {
    ......

    public int relayoutWindow(Session session, IWindow client,
            WindowManager.LayoutParams attrs, int requestedWidth,
            int requestedHeight, int viewVisibility, boolean insetsPending,
            Rect outFrame, Rect outContentInsets, Rect outVisibleInsets,
            Configuration outConfig, Surface outSurface) {
        ......

        synchronized(mWindowMap) {
            ......

            mInputMonitor.updateInputWindowsLw();
        }

        ......
    }

    ......
}

         这个函数又会继续调用mInputMonitor的updateInputWindowsLw成员函数来更新当前的输入窗口，mInputMonitor是WindowManagerService的成员变量，它的类型为InputMonitor。

 

         Step 5. InputMonitor.updateInputWindowsLw

         这个函数定义在frameworks/base/services/java/com/android/server/WindowManagerService.java 文件中：

public class WindowManagerService extends IWindowManager.Stub
        implements Watchdog.Monitor {
    ......

    final class InputMonitor {
        ......

        /* Updates the cached window information provided to the input dispatcher. */
        public void updateInputWindowsLw() {
            // Populate the input window list with information about all of the windows that
            // could potentially receive input.
            // As an optimization, we could try to prune the list of windows but this turns
            // out to be difficult because only the native code knows for sure which window
            // currently has touch focus.
            final ArrayList<WindowState> windows = mWindows;
            final int N = windows.size();
            for (int i = N - 1; i >= 0; i--) {
                final WindowState child = windows.get(i);
                if (child.mInputChannel == null || child.mRemoved) {
                    // Skip this window because it cannot possibly receive input.
                    continue;
                }

                ......

                // Add a window to our list of input windows.
                final InputWindow inputWindow = mTempInputWindows.add();

                ......
            }

            // Send windows to native code.
            mInputManager.setInputWindows(mTempInputWindows.toNullTerminatedArray());

            ......
        }

        ......
    }

    ......
}

        这个函数将当前系统中带有InputChannel的Activity窗口都设置为InputManager的输入窗口，但是后面我们会看到，只有当前激活的窗口才会响应键盘消息。

 

        Step 6. InputManager.setInputWindows

        这个函数定义在frameworks/base/services/java/com/android/server/InputManager.java文件中：

public class InputManager {
    ......

    public void setInputWindows(InputWindow[] windows) {
        nativeSetInputWindows(windows);
    }

    ......
}

        这个函数调用了本地方法nativeSetInputWindows来进一步执行操作。
        Step 7. InputManager.nativeSetInputWindows

 

        这个函数定义在frameworks/base/services/jni/com_android_server_InputManager.cpp 文件中：

static void android_server_InputManager_nativeSetInputWindows(JNIEnv* env, jclass clazz,
        jobjectArray windowObjArray) {
    if (checkInputManagerUnitialized(env)) {
        return;
    }

    gNativeInputManager->setInputWindows(env, windowObjArray);
}

        这里的gNativeInputManager我们前面分析InputManager的启动过程时已经见过了，这是一个本地InputManager对象，通过它进一步设置当前系统的输入窗口。