Android Input之JoyStick

一、配置文件

system/usr/keylayout/Generic.kl

......
# Joystick and game controller axes.
# Axes that are not mapped will be assigned generic axis numbers by the input subsystem.
axis 0x00 X
axis 0x01 Y
axis 0x02 Z
axis 0x03 RX
axis 0x04 RY
axis 0x05 RZ
axis 0x06 THROTTLE
axis 0x07 RUDDER
axis 0x08 WHEEL
axis 0x09 GAS
axis 0x0a BRAKE
axis 0x10 HAT_X
axis 0x11 HAT_Y

二、原理部分

ics/frameworks/base/core/java/android/view/ViewRootImpl.java

添加对axis 0x03 RX和axis 0x04 RY左边做上下左右按键的支持：

1.调用关系如下：

public void handleMotion(MotionEvent event, InputQueue.FinishedCallback finishedCallback) {
  ......
}
private void dispatchGenericMotion(MotionEvent event, boolean sendDone) {
  ......
}

public void handleMessage(Message msg) {
  ......
}
private void deliverGenericMotionEvent(MotionEvent event, boolean sendDone) {
  ......
}

2.核心代码片段

private void updateJoystickDirection(MotionEvent event, boolean synthesizeNewKeys) {
  ......
  int xDirection = joystickAxisValueToDirection(event.getAxisValue(MotionEvent.AXIS_HAT_X));
  if (xDirection == 0) {
    xDirection = joystickAxisValueToDirection(event.getX());
  }
  //add by tankai
  if (xDirection == 0) {
    xDirection = joystickAxisValueToDirection(event.getAxisValue(MotionEvent.AXIS_RX));
  }
  //end
  int yDirection = joystickAxisValueToDirection(event.getAxisValue(MotionEvent.AXIS_HAT_Y));
  if (yDirection == 0) {
    yDirection = joystickAxisValueToDirection(event.getY());
  }
  //add by tankai
  if (yDirection == 0) {
    yDirection = joystickAxisValueToDirection(event.getAxisValue(MotionEvent.AXIS_RY));
  }
  //end
  if (xDirection != mLastJoystickXDirection) {
    if (mLastJoystickXKeyCode != 0) {
      deliverKeyEvent(new KeyEvent(time, time,
                        KeyEvent.ACTION_UP, mLastJoystickXKeyCode, 0, metaState,
                        deviceId, 0, KeyEvent.FLAG_FALLBACK, source), false);
      mLastJoystickXKeyCode = 0;
    }
    mLastJoystickXDirection = xDirection;
    if (xDirection != 0 && synthesizeNewKeys) {
      mLastJoystickXKeyCode = xDirection > 0
                        ? KeyEvent.KEYCODE_DPAD_RIGHT : KeyEvent.KEYCODE_DPAD_LEFT;
      deliverKeyEvent(new KeyEvent(time, time,
                        KeyEvent.ACTION_DOWN, mLastJoystickXKeyCode, 0, metaState,
                        deviceId, 0, KeyEvent.FLAG_FALLBACK, source), false);
    }
  }

  if (yDirection != mLastJoystickYDirection) {
    if (mLastJoystickYKeyCode != 0) {
      deliverKeyEvent(new KeyEvent(time, time,
                        KeyEvent.ACTION_UP, mLastJoystickYKeyCode, 0, metaState,
                        deviceId, 0, KeyEvent.FLAG_FALLBACK, source), false);
      mLastJoystickYKeyCode = 0;
    }
    mLastJoystickYDirection = yDirection;
    if (yDirection != 0 && synthesizeNewKeys) {
      mLastJoystickYKeyCode = yDirection > 0
                        ? KeyEvent.KEYCODE_DPAD_DOWN : KeyEvent.KEYCODE_DPAD_UP;
      deliverKeyEvent(new KeyEvent(time, time,
                        KeyEvent.ACTION_DOWN, mLastJoystickYKeyCode, 0, metaState,
                        deviceId, 0, KeyEvent.FLAG_FALLBACK, source), false);
    }
  }
}