Android studio 如何客製化手势判定

记录每天学习到的内容-参考书第29章:Neil Smyth - Android Studio Electric Eel Essentials - Java Edition_ Developing Android Apps Using Android Studio 2022.1.1 and Java-Payload Media
如有错误欢迎指证

The GestureOverlayView Class

Android SDK 提供了GestureOverlayView 的class ，这是一个透明的view用于提供手势侦测。

侦测手势

注册一个GesturePerformedListener 事件监听器在GestureOverlayView class的实例上在外围的class implements OnGesturePerformedListener interface 以及对应的onGesturePerfomed callback函数
如果一个手势监听器侦测到，onGesturePerformed callback function会被Android runtime system 启用。

建立自定义的手势

开发工具Gesture Builder Tool在模拟器google play下载，以建立自定义的手势，模拟器档案管理在View -> Tool Windows -> Device File Explorer手势档(gesture.txt)会在以下模拟器中的位置。

/storage/emulated/0/Android/data/migueldp.runeforge/files/gestures.txt

将档案複製到专案中的res/raw里

使用者介面

在activity中建立GestureOverlayView 的layer
此範例中id设为gOverlay

<android.gesture.GestureOverlayViewandroid:id="@+id/gOverlay"android:layout_width="0dp"android:layout_height="0dp"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" />

读取手势档案

..import android.gesture.GestureOverlayView;import android.gesture.GestureOverlayView.OnGesturePerformedListener;import android.gesture.GestureLibraries;import android.gesture.GestureLibrary;public class MainActivity extends AppCompatActivity        implements OnGesturePerformedListener {            private ActivityMainBinding binding;    private GestureLibrary gLibrary;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        binding = ActivityMainBinding.inflate(getLayoutInflater());        setContentView(binding.getRoot());        gestureSetup();    }        private void gestureSetup() {        gLibrary = GestureLibraries.fromRawResource(this, R.raw.gestures);        if (!gLibrary.load()) {            finish();        }    }..}

除了之前讲到的 GestureOverlayView 以及OnGesturePerformedListener ，此程式建立了 GestureLibrary的实例gLibrary，用于载入位于res/raw里的手势档案，并且implement OnGesturePerformedListener interface，因此还会再往后补写onGesturePerformed callback function(因为是interface中的abstrack function)

注册OnGesturePerformedListener

为了让activity能收到使用者的手势，需要注册一个OnGesturePerformedListener到gLayout view 上，需增加以下程式码到gestureSetup()里面

GestureOverlayView gOverlay = findViewById(R.id.gOverlay);gOverlay.addOnGesturePerformedListener(this);

补写onGesturePerformed method

.import android.gesture.Prediction;import android.widget.Toast;import android.gesture.Gesture;import java.util.ArrayList;public class MainActivity extends AppCompatActivity implementsOnGesturePerformedListener {private GestureLibrary gLibrary;..    public void onGesturePerformed(GestureOverlayView overlay, Gesture    gesture) {        ArrayList<Prediction> predictions = gLibrary.recognize(gesture);        if (predictions.size() > 0 && predictions.get(0).score > 1.0)        {            String action = predictions.get(0).name;            Toast.makeText(this, action, Toast.LENGTH_SHORT).show();        }    }...}

多增加上述函式库4个函式库，当手势再gOverlay view 上被侦测到onGesturePerformed method被呼叫，同时传入一个GestureOverlayView 的物件以及被侦测到的手势(type: Gesture)，将侦测到的手势参数丢进gLibrary实例中的recognize()，目的是为了比较真测到的手势以及被从res/raw中读取到的手势档案，recognize()会回传一个ArrayList的物件包含一串Prediction物件，从最好排到最坏的预测，Prediction物件中包含了预测手势的名称以及预测分数。
在上述的程式码中判断手势是否评分大于1 ，如果满足条件，显示一个Toast message(显示弹跳通知)展示手势的名称

让手势变透明

在activity xml档中的android.gesture.GestureOverlayView增加最下面两行

<android.gesture.GestureOverlayViewandroid:id="@+id/gOverlay"android:layout_width="0dp"android:layout_height="0dp"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"android:gestureColor="#00000000"android:uncertainGestureColor="#00000000" />

侦测pinch手势(zoom in/ zoom out)

implements SimpleOnScaleGestureListener interface 需要複写
onScale(), onScaleBegin() and onScaleEnd() callback methods创造一个ScaleGestureDetector class的实例複写onTouchEvent() callback method 在最外围的activity

..import android.view.MotionEvent;import android.view.ScaleGestureDetector;import android.view.ScaleGestureDetector.SimpleOnScaleGestureListener;public class MainActivity extends AppCompatActivity {    private ActivityMainBinding binding;    ScaleGestureDetector scaleGestureDetector;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        binding = ActivityMainBinding.inflate(getLayoutInflater());        View view = binding.getRoot();        setContentView(view);        scaleGestureDetector = new ScaleGestureDetector(this,                                    new MyOnScaleGestureListener());                                        }        @Override    public boolean onTouchEvent(MotionEvent event) {        scaleGestureDetector.onTouchEvent(event);        return true;    }        public class MyOnScaleGestureListener extends    SimpleOnScaleGestureListener {        @Override        public boolean onScale(ScaleGestureDetector detector) {            float scaleFactor = detector.getScaleFactor();            if (scaleFactor > 1) {                binding.myTextView.setText("Zooming Out");            }             else {                binding.myTextView.setText("Zooming In");            }            return true;        }        @Override        public boolean onScaleBegin(ScaleGestureDetector detector) {            return true;        }                @Override        public void onScaleEnd(ScaleGestureDetector detector) {        }   }...}

参考书:Neil Smyth - Android Studio Electric Eel Essentials - Java Edition_ Developing Android Apps Using Android Studio 2022.1.1 and Java-Payload Media