谷歌眼镜GDK开发指南之触控手势

原文地址：http://bbs.seacat.cn/thread-900-1-1.html

可以通过Android sdk访问Glass触控板的原始数据。但GDK提供一个gesture detector ，可以自动识别通用手势，包括触摸、滑动和滚动。


通过D-pad keys识别手势

默认情况下，Glass系统会将简单的手势转换为D-pad keys事件。可以监听onKeyDown() 和 onKeyUp() 事件来处理D-pad keys：




1、触摸事件转义为 KEYCODE_DPAD_CENTER
2、相机按钮按下事件转义为 KEYCODE_CAMERA.
3、下滑事件转移为 KEYCODE_BACK


这是一小段触控事件的代码：

publicclass MyActivity extends Activity {
    ...
@Override
publicboolean onKeyDown(int keycode, KeyEvent event) {
if (keycode == KeyEvent.KEYCODE_DPAD_CENTER) {
// user tapped touchpad, do something
returntrue;
        }
        ...
returnfalse;
    }
}

通过gesture detector识别


使用gesture detector可以识别更多复杂的手势，例如多点触控或滚动。复杂的手势没有对应的D-pad key。

你可以实现 GestureDetector 提供的监听接口来通知 Gesture

识别activity层级的手势

1、创建一个 GestureDetector 的监听来处理识别的手势
2、重写activity的 onGenericMotionEvent() 方法，传入motion events给gesture detector的onMotionEvent()方法




当一个motion时间发生时，系统将它传给gesture detector。如果被识别了，gesture detector通知相关的监听接口来处理事件。

publicclass MainActivity extends Activity {
private GestureDetector mGestureDetector;
// ...
@Override
protectedvoid onCreate(Bundle savedInstanceState) {
// ...
        mGestureDetector = createGestureDetector(this);
    }

private GestureDetector createGestureDetector(Context context) {
    GestureDetector gestureDetector = new GestureDetector(context);
//Create a base listener for generic gestures
        gestureDetector.setBaseListener( new GestureDetector.BaseListener() {
@Override
publicboolean onGesture(Gesture gesture) {
if (gesture == Gesture.TAP) {
// do something on tap
returntrue;
                } elseif (gesture == Gesture.TWO_TAP) {
// do something on two finger tap
returntrue;
                } elseif (gesture == Gesture.SWIPE_RIGHT) {
// do something on right (forward) swipe
returntrue;
                } elseif (gesture == Gesture.SWIPE_LEFT) {
// do something on left (backwards) swipe
returntrue;
                }
returnfalse;
            }
        });
        gestureDetector.setFingerListener(new GestureDetector.FingerListener() {
@Override
publicvoid onFingerCountChanged(int previousCount, int currentCount) {
// do something on finger count changes
            }
        });
        gestureDetector.setScrollListener(new GestureDetector.ScrollListener() {
@Override
publicboolean onScroll(float displacement, float delta, float velocity) {
// do something on scrolling
            }
        });
return gestureDetector;
    }

/*
     * Send generic motion events to the gesture detector
     */
@Override
publicboolean onGenericMotionEvent(MotionEvent event) {
if (mGestureDetector != null) {
return mGestureDetector.onMotionEvent(event);
        }
returnfalse;
    }
}

识别view层级的手势

1、创建 一个自定义view并重写 dispatchGenericFocusedEvent() 方法。当一个motion 时间发生时，这个方法传入motion事件给gesture detector。


2、设置view为focusable ，以便当view获取焦点的时候能检测到事件。


3、创建一个 GestureDetector 的监听来处理识别的手势




当gesture detector识别到一个motion 的时候，gesture detector通知相关的监听接口来处理事件。

/**
 * TextView that handles touchpad input (currently only TAP).
 */
publicclass TouchpadHandlingTextView extends TextView
implements OnAttachStateChangeListener{

privatefinal GestureDetector mTouchDetector;

public TouchpadHandlingTextView(Context context, AttributeSet attrs) {
super(context, attrs);
        mTouchDetector = createGestureDetector(context);
// must set the view to be focusable
        setFocusable(true);
        setFocusableInTouchMode(true);
    }

public TouchpadHandlingTextView(Context context) {
this(context, null);
    }

@Override
publicvoid onViewAttachedToWindow(View v) {
        requestFocus();
    }

@Override
publicvoid onViewDetachedFromWindow(View v) {
    }

/**
     * Pass a MotionEvent into the gesture detector
     */
@Override
publicboolean dispatchGenericFocusedEvent(MotionEvent event) {
if (isFocused()) {
return mTouchDetector.onMotionEvent(event);
        }
returnsuper.dispatchGenericFocusedEvent(event);
    }

/**
     * Create gesture detector that triggers onClickListener. Implement
     * onClickListener in your Activity and override
     * onClick() to handle the "tap" gesture.
     */
private GestureDetector createGestureDetector(Context context) {
        GestureDetector gd = new GestureDetector(context);
        gd.setBaseListener(new GestureDetector.BaseListener() {

@Override
publicboolean onGesture(Gesture gesture) {
if (gesture == Gesture.TAP) {
return performClick();
                }
returnfalse;
            }
        });
return gd;
    }
}