谷歌眼鏡GDK開發指南之觸控手勢

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

可以通過Android sdk訪問Glass觸控板的原始數據。但GDK提供一個gesture detector ，可以自動識別通用手勢，包括觸摸、滑動和滾動。


通過D-pad keys識別手勢

默認情況下，Glass系統會將簡單的手勢轉換爲D-pad keys事件。可以監聽onKeyDown() 和 onKeyUp() 事件來處理D-pad keys：




1、觸摸事件轉義爲 KEYCODE_DPAD_CENTER
2、相機按鈕按下事件轉義爲 KEYCODE_CAMERA.
3、下滑事件轉移爲 KEYCODE_BACK


這是一小段觸控事件的代碼：

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

通過gesture detector識別


使用gesture detector可以識別更多複雜的手勢，例如多點觸控或滾動。複雜的手勢沒有對應的D-pad key。

你可以實現 GestureDetector 提供的監聽接口來通知 Gesture

識別activity層級的手勢

1、創建一個 GestureDetector 的監聽來處理識別的手勢
2、重寫activity的 onGenericMotionEvent() 方法，傳入motion events給gesture detector的onMotionEvent()方法




當一個motion時間發生時，系統將它傳給gesture detector。如果被識別了，gesture detector通知相關的監聽接口來處理事件。

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;
    }
}

識別view層級的手勢

1、創建 一個自定義view並重寫 dispatchGenericFocusedEvent() 方法。當一個motion 時間發生時，這個方法傳入motion事件給gesture detector。


2、設置view爲focusable ，以便當view獲取焦點的時候能檢測到事件。


3、創建一個 GestureDetector 的監聽來處理識別的手勢




當gesture detector識別到一個motion 的時候，gesture detector通知相關的監聽接口來處理事件。

/**
 * 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;
    }
}