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我的代码基本上来自这个例子（http://corner.squareup.com/2010/07/smooth-signatures.html）和谷歌API（FingerPaint），但现在我想使用这个类VelocityTracker来改变笔画宽度取决于以我手指的速度。

我以为我可以将路径分成更小的部分，但我没有找到任何示例。还有第二篇文章（http://corner.squareup.com/2012/07/smoother-signatures.html），但我既没有特定的贝塞尔曲线类，也没有收集所有点，ArrayList所以他们的例子是调整笔画宽度不是很有帮助。

有谁知道如何处理这个问题？我两周前开始学习代码，所以我对所有这些东西都很陌生。

编辑：我尝试实现 MotionEvents 的速度，并在运行应用程序时使用 LogCat 跟踪当前速度。它确实奏效了，但是当我尝试将速度用作 mPaint.setStrokeWidth 参数的一部分时，我没有得到我真正想要的。我在画布上绘制的路径的宽度从我开始画线到我向上移动手指的那一刻一直在变化。所以这就是为什么我想将路径分成更小的部分，因为就像现在一样，只有最后跟踪的速度会影响 strokeWidth。

public class SignatureView extends View {

    private static final String TAG = SignatureView.class.getSimpleName();
    private static final float STROKE_WIDTH = 10;
    private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
    private final double TOUCH_TOLERANCE = 5;
    private int h = getResources().getDisplayMetrics().heightPixels;
    private int w = getResources().getDisplayMetrics().widthPixels;

    private Path mPath = new Path();
    private Paint mPaint = new Paint();
    private Paint mBitmapPaint = new Paint(Paint.DITHER_FLAG);
    private Bitmap mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    private Canvas mCanvas = new Canvas(mBitmap);

    private float mX, mY;
    private float lastTouchX, lastTouchY;
    private final RectF dirtyRect = new RectF();

public SignatureView(Context context, AttributeSet attrs) {
    super(context, attrs);

    mPaint.setAntiAlias(true);
    mPaint.setColor(Color.BLACK);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeWidth(INITIAL_STROKE_WIDTH);

    Log.d(TAG, "TOUCH_TOLERANCE = " +TOUCH_TOLERANCE);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);            
    canvas.drawPath(mPath, mPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    float eventX = event.getX();
    float eventY = event.getY();
    int historySize = event.getHistorySize();

    switch (event.getAction()) {

        case MotionEvent.ACTION_DOWN:

            resetDirtyRect(eventX, eventY);
            mPath.reset();
            mPath.moveTo(eventX, eventY);
            mX = eventX;
            mY = eventY;
            break;

        case MotionEvent.ACTION_MOVE:

            float dx = Math.abs(eventX - mX);
            float dy = Math.abs(eventY - mY);

            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {

                mPath.quadTo(mX, mY, (eventX + mX)/2, (eventY + mY)/2);
                mX = eventX;
                mY = eventY;
            }

            for (int i = 0; i < historySize; i++) {
                float historicalX = event.getHistoricalX(i);
                float historicalY = event.getHistoricalY(i);
                expandDirtyRect(historicalX, historicalY);
            }
            break;

        case MotionEvent.ACTION_UP:

            for (int i = 0; i < historySize; i++) {
                float historicalX = event.getHistoricalX(i);
                float historicalY = event.getHistoricalY(i);
                expandDirtyRect(historicalX, historicalY);
            }

            mPath.lineTo(mX, mY);
            mCanvas.drawPath(mPath, mPaint);
            mPath.reset();
            break;

        default:
            Log.d(TAG, "Ignored touch event: " + event.toString());
        return false;
    }

    // Include half the stroke width to avoid clipping.
        invalidate(     (int) (dirtyRect.left - HALF_STROKE_WIDTH),
                        (int) (dirtyRect.top - HALF_STROKE_WIDTH),
                        (int) (dirtyRect.right + HALF_STROKE_WIDTH),
                        (int) (dirtyRect.bottom + HALF_STROKE_WIDTH));

    lastTouchX = eventX;
    lastTouchY = eventY;
    return true;
}

private void expandDirtyRect(float historicalX, float historicalY) {
    if (historicalX < dirtyRect.left) {
        dirtyRect.left = historicalX;
    } else if (historicalX > dirtyRect.right) {
        dirtyRect.right = historicalX;
    }
    if (historicalY < dirtyRect.top) {
        dirtyRect.top = historicalY;
    } else if (historicalY > dirtyRect.bottom) {
        dirtyRect.bottom = historicalY;
    }
}

private void resetDirtyRect(float eventX, float eventY) {

    dirtyRect.left = Math.min(lastTouchX, eventX);
    dirtyRect.right = Math.max(lastTouchX, eventX);
    dirtyRect.top = Math.min(lastTouchY, eventY);
    dirtyRect.bottom = Math.max(lastTouchY, eventY);
}
}
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1 回答 1

2

每次笔划值根据速度变化时，您都可以使用拆分路径对象。在你SignatureView的课堂上添加

private Path mPath = new Path();
ArrayList<Path> mPaths = new ArrayList<Path>();

并取另一个 ArrayList 来保持每个路径的笔画值

ArrayList<int> strokes = new ArrayList<int>();

lastStroke与lastTouchX和一起添加一个变量lastTouchY。我会推荐你​​ make lastStrokeof type int。

private int lastStroke = -1; //give an initial value

现在你的onTouchEvent方法应该是这样的

@Override
public boolean onTouchEvent(MotionEvent event) {
    float eventX = event.getX();
    float eventY = event.getY();
    int historySize = event.getHistorySize();
    int eventStroke= //calculate stroke size with velocity and make it between 1-10 or any range you seem fit

    switch (event.getAction()) {

        case MotionEvent.ACTION_DOWN:

            resetDirtyRect(eventX, eventY);
            mPath.reset();
            mPath.moveTo(eventX, eventY);
            mX = eventX;
            mY = eventY;
            break;

        case MotionEvent.ACTION_MOVE:

            float dx = Math.abs(eventX - mX);
            float dy = Math.abs(eventY - mY);

            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                if(lastStroke != evetnStroke){
                    mPath = new Path();
                    mPath.moveTo(mX,mY);
                    mPaths.Add(mPath);
                    mStrokes.Add(eventStroke);
                }
                mPath.quadTo(mX, mY, (eventX + mX)/2, (eventY + mY)/2);
                mX = eventX;
                mY = eventY;
            }

            for (int i = 0; i < historySize; i++) {
                float historicalX = event.getHistoricalX(i);
                float historicalY = event.getHistoricalY(i);
                expandDirtyRect(historicalX, historicalY);
            }
            break;

        case MotionEvent.ACTION_UP:

            for (int i = 0; i < historySize; i++) {
                float historicalX = event.getHistoricalX(i);
                float historicalY = event.getHistoricalY(i);
                expandDirtyRect(historicalX, historicalY);
            }

           mPath.lineTo(mX, mY);
           break;

        default:
            Log.d(TAG, "Ignored touch event: " + event.toString());
        return false;
    }
    // Include half the stroke width to avoid clipping.
    invalidate(     (int) (dirtyRect.left - HALF_STROKE_WIDTH),
                    (int) (dirtyRect.top - HALF_STROKE_WIDTH),
                    (int) (dirtyRect.right + HALF_STROKE_WIDTH),
                    (int) (dirtyRect.bottom + HALF_STROKE_WIDTH));

    lastTouchX = eventX;
    lastTouchY = eventY;
    lastStroke = eventStroke;
    return true;
}

你的 ondraw 方法是

@Override
protected void onDraw(Canvas canvas) {
    for(int i=0; i<mPaths.size();i++){
        mPaint.setStrokeWidth(strokes.get(i));
        canvas.drawPath(mPaths.get(i), mPaint);
    }
}

这是基本思想。您需要对其进行修改以使其正常工作。

于 2013-03-20T20:06:00.037 回答