添加触控支持

要处理触摸输入事件，请在游戏循环中读取数组 motionEvents。这些包含自上次清除这些数组以来发生的事件。包含的事件数存储在 motionEventsCount 中。

在游戏循环中迭代和处理每个事件。在此示例中，以下代码迭代 motionEvents 并通过 handle_event 处理它们

for(size_t i = 0; i < mApp->motionEventsCount; ++i) {
  GameActivityMotionEvent* motionEvent = mApp->motionEvents[i];

  int action = motionEvent->action;
  int actionMasked = action & AMOTION_EVENT_ACTION_MASK;
  int ptrIndex = (action & AMOTION_EVENT_ACTION_POINTER_INDEX_MASK) >>
    AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT;

  struct CookedEvent ev;
  memset(&ev, 0, sizeof(ev));

  if (actionMasked == AMOTION_EVENT_ACTION_DOWN ||
    actionMasked == AMOTION_EVENT_ACTION_POINTER_DOWN) {
      ev.type = COOKED_EVENT_TYPE_POINTER_DOWN;
  } else if (actionMasked == AMOTION_EVENT_ACTION_UP ||
    actionMasked == AMOTION_EVENT_ACTION_POINTER_UP) {
      ev.type = COOKED_EVENT_TYPE_POINTER_UP;
  } else {
      ev.type = COOKED_EVENT_TYPE_POINTER_MOVE;
  }

  ev.motionPointerId = motionEvent->pointers[ptrIndex].id;
  ev.motionIsOnScreen = motionEvent->source == AINPUT_SOURCE_TOUCHSCREEN;
  ev.motionX = GameActivityPointerInfo_getX(
    &motionEvent->pointers[ptrIndex]);
  ev.motionY = GameActivityPointerInfo_getY(
    &motionEvent->pointers[ptrIndex]);

  if (ev.motionIsOnScreen) {
    // Use screen size as the motion range.
    ev.motionMinX = 0.0f;
    ev.motionMaxX = SceneManager::GetInstance()->GetScreenWidth();
    ev.motionMinY = 0.0f;
    ev.motionMaxY = SceneManager::GetInstance()->GetScreenHeight();
  }

  handle_event(&ev);
}

完成后，请务必清除您刚刚处理过的事件队列
```
android_app_clear_motion_events(mApp);
```