我如何画一个箭头（Android中）？ [英] How do I draw an arrowhead (in Android)?

问题描述

我是相当新的Andr​​oid和被玩弄周围的画布。我试图画一个箭头，但我只是有运气绘制轴，没有箭头的正常工作。

I'm fairly new to Android and have been toying around with Canvas. I'm attempting to draw an arrow but I'm only having luck with drawing the shaft, none of the arrowhead is working.

我已经搜索了一下，发现一个Java的例子，但是Android不具备的GeneralPath 或的AffineTransform 。

I have searched a bit and found a Java example, but Android doesn't have GeneralPath or AffineTransform.

现在我的code如下所示（箭头看上去一点也不像一个箭头）：

Right now my code looks like the following (the arrowhead looks nothing like an arrowhead):

public class DrawableView extends View {
    Context mContext;
    private int centerX;
    private int centerY;
    private int radius;
    private double arrLength;
    private double arrHeading;
    private int margin = 10;

    public DrawableView(Context context) {
        super(context);
        mContext = context;
    }


    @Override
    protected void onDraw(Canvas canvas) {
        //Paint Background
        Paint background = new Paint();
        background.setColor(getResources().getColor(R.color.background);
        canvas.drawRect(0, 0, getWidth(), getHeight(), background);

        //Set vars for Arrow Paint
        Paint paint = new Paint();
        paint.setColor(getResources().getColor(R.color.arrowColor);
        centerX = getWidth() / 2;
        centerY = getHeight() / 2;
        arrLength = radius - 10;

        if(centerX < centerY)
            radius = centerX - margin;
        else 
            radius = centerY - margin;

        //Draw Shaft
        int[] xy = findArrowPos(arrLength, arrHeading);
        canvas.drawLine(centerX, centerY, xy[0], xy[1], paint);

        //Draw ArrowHead
            //This is where I'm confused

    }

    private int[] findArrowPos(double length, double angle) {
        int[] points = new int[2];
        double theta = Math.toRadians(angle);
        points[0] = centerX + (int) (length * Math.cos(theta));
        points[1] = centerY + (int) (length * Math.sin(theta));
        return points;
    }
}

我已经采取了看看指导以下主题：
 *的http://www.java-forums.org/awt-swing/6241-how-u-rotate-arrow-mark-line-moves-accordingly.html
 * 如何绘制的Java？

I have taken a look at the following threads for guidance:
* http://www.java-forums.org/awt-swing/6241-how-u-rotate-arrow-mark-line-moves-accordingly.html
* How to draw a directed arrow line in Java?

推荐答案

有关如何使用路径mypath中=新路径（）;在这里，你会得到x和y的位置，以创建一个使用线条和填充它的三角形。你可以阅读一下，这里是一个例子，我从什么地方了。

How about using "Path myPath = new Path();" where you would give the x and y positions to create a triangle using lines and filling it. You can read about it, here is an example I took from somewhere.

// create and draw triangles
// use a Path object to store the 3 line segments
// use .offset to draw in many locations
// note: this triangle is not centered at 0,0
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.RED);
Path path = new Path();
path.moveTo(0, -10);
path.lineTo(5, 0);
path.lineTo(-5, 0);
path.close();
path.offset(10, 40);
canvas.drawPath(path, paint);
path.offset(50, 100);
canvas.drawPath(path, paint);
// offset is cumlative
// next draw displaces 50,100 from previous
path.offset(50, 100);
canvas.drawPath(path, paint);

这篇关于我如何画一个箭头（Android中）？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！