如何让路线绘制更高效? [英] How to make route drawing more efficient?

问题描述

这是我用来绘制路线的代码.当我有 1000 个点时，路线会严重减慢 ui.也许有人可以提供一个代码片段或一个链接来解释如何更有效地绘制路线?我知道解决这个问题的一种方法是缓存位图的路径，但不知道该怎么做.

This is the code I'm using to draw route. When i have 1000 of points, route severely slows ui. Maybe someone could provide a code snippet or a link which explains how to do route drawing more efficiently? I know that one way to solve this is caching path to bitmap, but have no idea how to do it.

public class PathOverlay extends Overlay{

private GeoPoint startPoint;
private GeoPoint finishPoint;
private ArrayList<GeoPoint> pathPoints;
private Paint paint;
private Path path;
private Point pathStartPoint;
private Point pathEndPoint;

private float dx;
private float dy;


public PathOverlay(GeoPoint startPoint, GeoPoint finishPoint, ArrayList<GeoPoint> pathPoints, int color){
    this.startPoint = startPoint;
    this.finishPoint = finishPoint;
    this.pathPoints = pathPoints;
    this.paint = new Paint();
    this.paint.setAntiAlias(true);
    this.paint.setDither(true);
    this.paint.setColor(color);
    this.paint.setAlpha(150);
    this.paint.setStrokeWidth(4);
    this.paint.setStyle(Paint.Style.STROKE);
}

@Override
public void draw(Canvas overlayCanvas, MapView mapView, boolean shadow) {
    if(path == null) {
        path = getPath(mapView);
    } else {
        path = transformPath(mapView);
    }
    overlayCanvas.drawPath(path, paint);
    super.draw(overlayCanvas, mapView, shadow);
}

private Path getPath(MapView mapView) {
    Projection projection = mapView.getProjection();
    if(path == null) {
        path = new Path();
        path.setFillType(FillType.WINDING);
    } else {
        path.rewind();
    }
    Point point = new Point();
    pathStartPoint = new Point();
    pathEndPoint = new Point();

    projection.toPixels(startPoint, point);
    projection.toPixels(startPoint, pathStartPoint);
    path.moveTo(point.x, point.y);
    path.addCircle(point.x, point.y, (float) 2.0, Direction.CCW);
    if (pathPoints != null) {
        for(int i=0;i<pathPoints.size();i++) {
            projection.toPixels(pathPoints.get(i), point);
            path.lineTo(point.x, point.y);
        }
    }
    projection.toPixels(finishPoint, point);
    projection.toPixels(finishPoint, pathEndPoint);
    path.lineTo(point.x-5, point.y);
    path.addCircle(point.x-5, point.y, (float) 2.0, Direction.CCW);


    return path;
}

private Path transformPath(MapView mapView) {
    Projection projection = mapView.getProjection();

    Point sPoint = new Point();
    Point ePoint = new Point();
    projection.toPixels(startPoint, sPoint);
    projection.toPixels(finishPoint, ePoint);

    float sx = ((float)ePoint.x - (float)sPoint.x)/((float)pathEndPoint.x - (float)pathStartPoint.x);
    float sy = ((float)ePoint.y - (float)sPoint.y)/((float)pathEndPoint.y - (float)pathStartPoint.y);

    if(sx != 1.0 && sy != 1.0) {
        Log.i("PathOverlay", "resized");
        return getPath(mapView);
    } else {
        Log.i("PathOverlay", "moved");
        Matrix matrix = new Matrix();

        dx = (float)sPoint.x - (float)pathStartPoint.x;
        dy = (float)sPoint.y - (float)pathStartPoint.y;

        matrix.postTranslate(dx, dy);
        pathStartPoint = sPoint;
        pathEndPoint = ePoint;
        path.transform(matrix);

        return path;
    }
}

}

推荐答案

您可以绘制透明 Bitmap 对象的路径(无论您认为合适的大小 - 越大，细节越好的路径但内存消耗更高).

You can draw the path to a transparent Bitmap object (whatever size you see fitting - the bigger it is, the better the detail of the path yet higher memory consumption).

确保使用 Bitmap.config.ARGB_8888 创建它以实现透明度.

Make sure you create it with Bitmap.config.ARGB_8888 for transparency.

完成此操作后，您将使用两个矩形在 Overlay 上显示路径:

Once you've done this, you'll be using two rectangles to display the path on the Overlay:

• 用于确定路径的哪一部分可见的源矩形
• 一个目标矩形，用于确定要在 Overlay 的画布上显示这条路径的位置.

• A source rectangle to determine which part of the path is visible
• A destination rectangle to determine where you want to display this piece of the path on the Overlay's canvas.

您将使用 Canvas.drawBitmap(位图位图, Rect src, RectF dst, Paint Paint)

应该不会太难，您已经在 transformPath 方法中完成了大部分重要计算.

Shouldn't be too difficult, you've done most of the important calculations in your transformPath method.

添加:

实际上，您可以结合使用绘制到位图的路径和重新绘制实际路径点.当用户在地图上移动或放大/缩小时使用上述技术，然后在用户松开屏幕时重新绘制路径.

You can actually do a combination of both holding a path drawn to a Bitmap and redrawing the actual path points. Use the technique described above for when the user moves around the map or zooms in/out then redraw the path when the user lets go of the screen.

这篇关于如何让路线绘制更高效?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！