在屏幕上的Andr​​oid图形对象和获取几何数据 [英] Android drawing objects on screen and obtaining geometry data

问题描述

对图形对象的任何经验，例如顶点多边形并获得其表面和周长。

Has anybody experience on drawing objects, by vertices e.g. Polygons and obtaining their surface and perimeter.

几何将通过手工使用顶点绘制坐标或类似的 https://play.google.com/store/apps/details?id=de.hms.xconstruction 然后形状形成。我需要获得这些封闭形状的表面。

The geometry will be drawn by hand using vertices or coordinates similar to https://play.google.com/store/apps/details?id=de.hms.xconstruction and then shapes formed. I need to obtain the surface of these closed shapes.

有没有在网络上任何可用的例子吗？

Is there any available example on the net?

先谢谢了。

推荐答案

我觉得以下code的一块可能是一个良好的开端。它基本上把一切用户触摸的行：

I think the following piece of code could be a good start. It basically draws lines between all user touches:

public class TestActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(new DrawingView(this));
}

class DrawingView extends SurfaceView {

    private final SurfaceHolder surfaceHolder;
    private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

    private List<Point> pointsList = new ArrayList<Point>();

    public DrawingView(Context context) {
        super(context);
        surfaceHolder = getHolder();
        paint.setColor(Color.WHITE);
        paint.setStyle(Style.FILL);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            if (surfaceHolder.getSurface().isValid()) {

                // Add current touch position to the list of points
                pointsList.add(new Point((int)event.getX(), (int)event.getY()));

                // Get canvas from surface
                Canvas canvas = surfaceHolder.lockCanvas();

                // Clear screen
                canvas.drawColor(Color.BLACK);

                // Iterate on the list
                for(int i=0; i<pointsList.size(); i++) {
                    Point current = pointsList.get(i);

                    // Draw points
                    canvas.drawCircle(current.x, current.y, 10, paint);

                    // Draw line with next point (if it exists)
                    if(i + 1 < pointsList.size()) {
                        Point next = pointsList.get(i+1);
                        canvas.drawLine(current.x, current.y, next.x, next.y, paint);
                    }
                }

                // Release canvas
                surfaceHolder.unlockCanvasAndPost(canvas);
            }
        }
        return false;
    }

}

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