Instrumentation事件注入机制

通过sendevent原始事件注入
 原始事件注入可以通过eventhub的sendevent()注入。
 adb命令： adb shell sendevent /dev/input/event0 <类型><代码> <值>

通过Instrumentation事件注入
 Instrumentation的事件注入本质上还是通过InputDispatcher注入的，没有经过eventHub。
调用链
----Instrumentation.sendStringSync
--------Instrumentation.sendKeySync
------------InputManager.getInstance().injectInputEvent
----------------InputManagerService.injectInputEvent
--------------------InputManagerService.injectInputEventInternal
------------------------InputManagerService.nativeInjectInputEvent
----------------------------InputDispatcher.injectInputEvent

/frameworks/base/core/java/android/app/Instrumentation.java

/**
 * Sends the key events corresponding to the text to the app being
 * instrumented.
 * @param text The text to be sent. 
 */
public void sendStringSync(String text) {
    if (text == null) {
        return;
    }
    KeyCharacterMap keyCharacterMap = KeyCharacterMap.load(KeyCharacterMap.VIRTUAL_KEYBOARD);

    KeyEvent[] events = keyCharacterMap.getEvents(text.toCharArray());

    if (events != null) {
        for (int i = 0; i < events.length; i++) {
            // We have to change the time of an event before injecting it because
            // all KeyEvents returned by KeyCharacterMap.getEvents() have the same
            // time stamp and the system rejects too old events. Hence, it is
            // possible for an event to become stale before it is injected if it
            // takes too long to inject the preceding ones.
            sendKeySync(KeyEvent.changeTimeRepeat(events[i], SystemClock.uptimeMillis(), 0));
        }
    }
}

/**
 * Send a key event to the currently focused window/view and wait for it to
 * be processed.  Finished at some point after the recipient has returned
 * from its event processing, though it may <em>not</em> have completely
 * finished reacting from the event -- for example, if it needs to update
 * its display as a result, it may still be in the process of doing that.
 * @param event The event to send to the current focus.
 */
public void sendKeySync(KeyEvent event) {
    validateNotAppThread();

    long downTime = event.getDownTime();
    long eventTime = event.getEventTime();
    int action = event.getAction();
    int code = event.getKeyCode();
    int repeatCount = event.getRepeatCount();
    int metaState = event.getMetaState();
    int deviceId = event.getDeviceId();
    int scancode = event.getScanCode();
    int source = event.getSource();
    int flags = event.getFlags();
    if (source == InputDevice.SOURCE_UNKNOWN) {
        source = InputDevice.SOURCE_KEYBOARD;
    }
    if (eventTime == 0) {
        eventTime = SystemClock.uptimeMillis();
    }
    if (downTime == 0) {
        downTime = eventTime;
    }
    KeyEvent newEvent = new KeyEvent(downTime, eventTime, action, code, repeatCount, metaState,
            deviceId, scancode, flags | KeyEvent.FLAG_FROM_SYSTEM, source);
    InputManager.getInstance().injectInputEvent(newEvent,
            InputManager.INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH);
}