http://marakana.com/tutorials/android/2d-graphics-example.html

我使用下面这个例子。但是，当我将我的手指过快在屏幕上线变为单个点。

I am using this example below. But when I move my fingers too fast across the screen the line turns to individual dots.

我不知道我是否能够加速绘图。或者我应该用直线连接这两个最后点。这两种解决方案的第二个似乎是个不错的选择，移动你的手指时，速度非常快，你将有一个直线长款则急转弯的除外。

I am not sure whether I can speed up the drawing. Or I should connect the two last points with a straight line. The second of these two solutions seems like a good option, except when moving your finger very fast you will have long sections of a straight line then sharp curves.

如果有任何其他的解决方案，这将是巨大的，听到他们的声音。

If there are any other solutions it would be great to hear them.

感谢提前任何帮助。

推荐答案

这是简单的解决方案，正如你所说，是简单地用直线连接点。这里的code这样做的：

An easy solution, as you mentioned, is to simply connect the points with a straight line. Here's the code to do so:

public void onDraw(Canvas canvas) {
    Path path = new Path();
    boolean first = true;
    for(Point point : points){
        if(first){
            first = false;
            path.moveTo(point.x, point.y);
        }
        else{
            path.lineTo(point.x, point.y);
        }
    }
    canvas.drawPath(path, paint);
}

请确保您填写更改您的油漆中风：

make sure you change your paint from fill to stroke:

paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.WHITE);

另一种方法是用iterpolation使用quadTo方法连接点：

Another option is to connect the points with iterpolation using the quadTo method:

public void onDraw(Canvas canvas) {
    Path path = new Path();
    boolean first = true;
    for(int i = 0; i < points.size(); i += 2){
        Point point = points.get(i);
        if(first){
            first = false;
            path.moveTo(point.x, point.y);
        }

        else if(i < points.size() - 1){
            Point next = points.get(i + 1);
            path.quadTo(point.x, point.y, next.x, next.y);
        }
        else{
            path.lineTo(point.x, point.y);
        }
    }

    canvas.drawPath(path, paint);
}

这仍然导致了一些尖锐的边缘。

This still results in some sharp edges.

如果你真的雄心勃勃，你就可以开始计算的三次样条函数如下：

If you're really ambitious, you can start to calculate the cubic splines as follows:

public void onDraw(Canvas canvas) {
    Path path = new Path();

    if(points.size() > 1){
        for(int i = points.size() - 2; i < points.size(); i++){
            if(i >= 0){
                Point point = points.get(i);

                if(i == 0){
                    Point next = points.get(i + 1);
                    point.dx = ((next.x - point.x) / 3);
                    point.dy = ((next.y - point.y) / 3);
                }
                else if(i == points.size() - 1){
                    Point prev = points.get(i - 1);
                    point.dx = ((point.x - prev.x) / 3);
                    point.dy = ((point.y - prev.y) / 3);
                }
                else{
                    Point next = points.get(i + 1);
                    Point prev = points.get(i - 1);
                    point.dx = ((next.x - prev.x) / 3);
                    point.dy = ((next.y - prev.y) / 3);
                }
            }
        }
    }

    boolean first = true;
    for(int i = 0; i < points.size(); i++){
        Point point = points.get(i);
        if(first){
            first = false;
            path.moveTo(point.x, point.y);
        }
        else{
            Point prev = points.get(i - 1);
            path.cubicTo(prev.x + prev.dx, prev.y + prev.dy, point.x - point.dx, point.y - point.dy, point.x, point.y);
        }
    }
    canvas.drawPath(path, paint);
}

另外，我发现你需要改变以下，以避免出现重复的动作事件：

Also, I found that you needed to change the following to avoid duplicate motion events:

public boolean onTouch(View view, MotionEvent event) {
    if(event.getAction() != MotionEvent.ACTION_UP){
        Point point = new Point();
        point.x = event.getX();
        point.y = event.getY();
        points.add(point);
        invalidate();
        Log.d(TAG, "point: " + point);
        return true;
    }
    return super.onTouchEvent(event);
}

和添加DX和放大器; DY值Point类：

and add the dx & dy values to the Point class:

class Point {
    float x, y;
    float dx, dy;

    @Override
    public String toString() {
        return x + ", " + y;
    }
}

这会产生流畅的线条，但有时也有使用循环连接点。 此外，长期绘画会议，这成为计算密集型计算。

This produces smooth lines, but sometimes has to connect the dots using a loop. Also, for long drawing sessions, this becomes computationally intensive to calculate.

希望有所帮助......有趣的东西玩弄。

Hope that helps... fun stuff to play around with.

修改

我扔一起快速的项目演示这些不同的技术，其中包括Square的suggessted签名实现。享受： https://github.com/johncarl81/androiddraw

I threw together a quick project demonstrating these different techniques, including Square's suggessted signature implementation. Enjoy: https://github.com/johncarl81/androiddraw