Android 源码 InputManagerService 启动

上一节分析了 InputManagerService 初始化，这一节重点关注启动以后都做了一些什么？

frameworks/base/services/java/com/android/server/SystemServer.java

public final class SystemServer {
    ......
    public static void main(String[] args) {
        new SystemServer().run();
    }
    ......
    private void run() {
        ......
        try {
            ......
            startOtherServices();
        } catch (Throwable ex) {
            ......
        }
        ......
    }
    ......
    private void startOtherServices() {
        ......
        WindowManagerService wm = null;
        ......
        InputManagerService inputManager = null;
        ......
        try {
            ......
            // 启动 InputManagerService
            inputManager.start();
            ......
        } catch (RuntimeException e) {
            ......
        }
    }
    ......
}

InputManagerService start 方法完成了 InputManagerService 启动。把获取到的输入事件进行处理，最后分发给对应的处理窗口，或者拦截到相应处理过程中进行处理。nativeStart 从方法名可知是做一些 native 启动工作的， mPtr 是指向 native input manager 服务对象的指针。

frameworks/base/services/core/java/com/android/server/input/InputManagerService.java

public class InputManagerService extends IInputManager.Stub
        implements Watchdog.Monitor {
    ......
    public void start() {
        Slog.i(TAG, "Starting input manager");
        // mPtr 是指向 native input manager 服务对象的指针
        nativeStart(mPtr);

        // 添加到看门狗监视器
        Watchdog.getInstance().addMonitor(this);

        ......
    }
    ......
}

首先将传递过来的 jlong 转化为 NativeInputManager 指针，接着调用其 getInputManager() 获取 InputManager 对象，最后调用 InputManager 的 start 方法。

frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp

static void nativeStart(JNIEnv* env, jclass /* clazz */, jlong ptr) {
    NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);

    status_t result = im->getInputManager()->start();
    if (result) {
        jniThrowRuntimeException(env, "Input manager could not be started.");
    }
}

getInputManager 函数是一个内联函数。

frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp

class NativeInputManager : public virtual RefBase,
    public virtual InputReaderPolicyInterface,
    public virtual InputDispatcherPolicyInterface,
    public virtual PointerControllerPolicyInterface {
    ......
public:
    ......
    inline sp<InputManager> getInputManager() const { return mInputManager; }
    ......
private:
    sp<InputManager> mInputManager;
    ......
};

1.启动 DispatcherThread；

2.启动 ReaderThread。

frameworks/native/services/inputflinger/InputManager.cpp

status_t InputManager::start() {
    // 1.启动 DispatcherThread
    status_t result = mDispatcherThread->run("InputDispatcher", PRIORITY_URGENT_DISPLAY);
    if (result) {
        ALOGE("Could not start InputDispatcher thread due to error %d.", result);
        return result;
    }
    // 2.启动 ReaderThread
    result = mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY);
    if (result) {
        ALOGE("Could not start InputReader thread due to error %d.", result);
        // 请求退出 DispatcherThread
        mDispatcherThread->requestExit();
        return result;
    }

    return OK;
}

到了这一步， InputManagerService 就跑起来了，InputReaderThread 负责读取输入事件，InputDispatcherThread 负责派发事件到当前窗口进行处理。如果 InputReaderThread 启动失败，则调用 InputDispatcherThread requestExit 方法请求退出派发事件线程。