我要一步一步往上爬——Android应用实例笔记(1)—手势

我要一步一步往上爬——Android应用实例笔记(1)

 

源程序来自APIDemo的GestureBuilder

 

• 相关的类

Gesture

 

A gesture is a hand-drawn shape on a touch screen. It can have one or multiple strokes.

Each stroke is a sequence of timed points.

A user-defined gesture can be recognized by a GestureLibrary and a built-in alphabet gesture can be recognized by a LetterRecognizer.

1. 一个手势就是一个在触摸屏幕的手写形状。它可以有一个或者多个笔画。每个笔画是由一些列的时序点构成。

 

一个用户自定义的手势可以被GestureLibrary 识别，或者字母手势可以被内置的字符识别器（ LetterRecognizer）识别

 

GestureLibrary

用于添加存储获取Getsture的管理容器。通常由GestureLibraries的如下4个方法来获得，

 

 

static GestureLibrary	fromFile(File path)
static GestureLibrary	fromFile(String path)
static GestureLibrary	fromPrivateFile(Context context, String name)
static GestureLibrary	fromRawResource(Context context, int resourceId)

 

GestureOverLayView

 

GestureOverLayView,一个用于输入的透明层，它可以放到任何widget层上或者任何包含其他widget组件，即在最上层。

 

 GestureOverLayView可以添加手势识别监听器：如下面

 

 GestureOverlayView overlay = (GestureOverlayView) findViewById(R.id.gestures_overlay);
        //添加手势识别监听器。
        overlay.addOnGestureListener(new GesturesProcessor());

 

GestureOverlayView.OnGestureListener

 用于监听手势，需要实现onGesture，onGestureEnded这两个方法

 

源程序注释：

 

public class CreateGestureActivity extends Activity {
    private static final float LENGTH_THRESHOLD = 120.0f;

    private Gesture mGesture;
    private View mDoneButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       
        setContentView(R.layout.create_gesture);

        mDoneButton = findViewById(R.id.done);
        //GestureOverLayView,一个用于输入的透明层，它可以放到任何widget层上或者任何包含其他widget组件。
        GestureOverlayView overlay = (GestureOverlayView) findViewById(R.id.gestures_overlay);
        //添加手势识别监听器。
        overlay.addOnGestureListener(new GesturesProcessor());
    }

    //用来检索存储每个对象实例化当前状态，在Activity被kill掉之前前被调用，可以被onCreate(Bundle) 或者 onRestoreInstanceState(Bundle) 调用恢复对象状态。
   
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
       
        if (mGesture != null) {
            outState.putParcelable("gesture", mGesture);
        }
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        //恢复上一次手势
        mGesture = savedInstanceState.getParcelable("gesture");
        if (mGesture != null) {
            final GestureOverlayView overlay =
                    (GestureOverlayView) findViewById(R.id.gestures_overlay);
            overlay.post(new Runnable() {
                public void run() {
                    overlay.setGesture(mGesture);
                }
            });

            mDoneButton.setEnabled(true);
        }
    }

    //添加手势
    @SuppressWarnings({"UnusedDeclaration"})
    public void addGesture(View v) {
        if (mGesture != null) {
            final TextView input = (TextView) findViewById(R.id.gesture_name);
            final CharSequence name = input.getText();
            if (name.length() == 0) {
                input.setError(getString(R.string.error_missing_name));
                return;
            }

            //GestureLibraries.fromFile(mStoreFile);GestureLibraries可以有多种方式构造GestureLibrary
            //fromPrivateFile (Context context, String name)
            //fromRawResource (Context context, int resourceId)
            //A gesture is a hand-drawn shape on a touch screen. It can have one or multiple strokes. Each stroke is a sequence of timed points. A user-defined gesture can be recognized by a GestureLibrary.
            //一个手势是手在触摸屏上划动形成的轨迹，它可以有一个或多个曲线，每个曲线是一按时间序列的点。GestureLibrary可以识别用户定义的手势
            final GestureLibrary store = GestureBuilderActivity.getStore();
            store.addGesture(name.toString(), mGesture);//将手势添加到自定义的手势库中，并保存
            store.save();

            setResult(RESULT_OK);

            final String path = new File(Environment.getExternalStorageDirectory(),
                    "gestures").getAbsolutePath();
            Toast.makeText(this, getString(R.string.save_success, path), Toast.LENGTH_LONG).show();
        } else {
            setResult(RESULT_CANCELED);
        }

        finish();
       
    }
   
    @SuppressWarnings({"UnusedDeclaration"})
    public void cancelGesture(View v) {
        setResult(RESULT_CANCELED);
        finish();
    }
   
    //监听Gesture事件监听器,类似的还有OnGesturePerformedListener
    //GestureOverlayView.OnGesturingListener,这个处理手势刚开始，和结束事件

    private class GesturesProcessor implements GestureOverlayView.OnGestureListener {
        public void onGestureStarted(GestureOverlayView overlay, MotionEvent event) {
            mDoneButton.setEnabled(false);
            mGesture = null;
        }

        @Override
        public void onGesture(GestureOverlayView overlay, MotionEvent event) {
        }
        @Override
        public void onGestureEnded(GestureOverlayView overlay, MotionEvent event) {
            mGesture = overlay.getGesture();

//这里过滤比较短的笔画或者曲线
            if (mGesture.getLength() < LENGTH_THRESHOLD) {
                overlay.clear(false);
            }

//获得所有笔画
        List<GestureStroke> strokes= mGesture.getStrokes();
           
            for(GestureStroke stroke:strokes){
             OrientedBoundingBox orientedBoundingBox=stroke.computeOrientedBoundingBox();
             Path path = stroke.getPath();
             path.setFillType(FillType.INVERSE_EVEN_ODD);//填充方式为奇偶填充。这个可以参见填充方式

             for(float p:stroke.points){
              System.out.print(p+' ');
             }
            }
            mDoneButton.setEnabled(true);
        }

        public void onGestureCancelled(GestureOverlayView overlay, MotionEvent event) {
        }
    }
}