Android输入系统（二）——IMS启动过程（基于Android 13）

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已于 2023-06-28 22:09:07 修改 · 1.3k 阅读

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于 2022-09-20 09:08:04 首次发布

1 IMS启动过程

IMS的启动还是从SystemServer的startOtherServices方法中启动的。
frameworks/native/services/inputflinger/reader/InputReader.cpp

private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
   
   
	...
	t.traceBegin("StartInputManager");
	inputManager.setWindowManagerCallbacks(wm.getInputManagerCallback());
	inputManager.start();
	t.traceEnd();
	...
}

这里调用InputManagerService的start方法。
frameworks/native/services/inputflinger/reader/InputReader.cpp

public void start() {
   
   
    Slog.i(TAG, "Starting input manager");
    mNative.start(); //1

    // Add ourselves to the Watchdog monitors.
    Watchdog.getInstance().addMonitor(this); //2

    registerPointerSpeedSettingObserver();
    registerShowTouchesSettingObserver();
    registerAccessibilityLargePointerSettingObserver();
    registerLongPressTimeoutObserver();
    registerMaximumObscuringOpacityForTouchSettingObserver();
    registerBlockUntrustedTouchesModeSettingObserver();

    mContext.registerReceiver(new BroadcastReceiver() {
   
   
        @Override
        public void onReceive(Context context, Intent intent) {
   
   
            updatePointerSpeedFromSettings();
            updateShowTouchesFromSettings();
            updateAccessibilityLargePointerFromSettings();
            updateDeepPressStatusFromSettings("user switched");
        }
    }, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mHandler);

    updatePointerSpeedFromSettings();
    updateShowTouchesFromSettings();
    updateAccessibilityLargePointerFromSettings();
    updateDeepPressStatusFromSettings("just booted");
    updateMaximumObscuringOpacityForTouchFromSettings();
    updateBlockUntrustedTouchesModeFromSettings();
}

注释1处调用native的start方法，注释2处将自身添加到watchdog中进行监测。
frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp

static void nativeStart(JNIEnv* env, jobject nativeImplObj) {
   
   
    NativeInputManager* im = getNativeInputManager(env, nativeImplObj);

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

这里获取native中的InputManager对象，并调用其中的start方法。
frameworks/native/services/inputflinger/InputManager.cpp

status_t InputManager::start() {
   
   
    status_t result = mDispatcher->start(); //1
    if (result) {
   
   
        ALOGE("Could not start InputDispatcher thread due to error %d.", result);
        return result;
    }

    result = mReader->start(); //2
    if (result) {
   
   
        ALOGE("Could not start InputReader due to error %d.", result);

        mDispatcher->stop();
        return result;
    }

    return OK;
}

注释1处调用了InputDispatcher的start函数，注释2处调用了InputReader的start函数。

2 InputDispatcher的启动

由上面的InputManager的start方法中调用了InputDispatcher的start函数。
frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp

status_t InputDispatcher::start() {
   
   
    if (mThread) {
   
   
        return ALREADY_EXISTS;
    }
    mThread = std::make_unique<InputThread>(
            "InputDispatcher", [this]() {
   
    dispatchOnce(); }, [this