Question

我通过画布上的某些坐标绘制路径和标记，在画面上显示图像。在图片上的某个坐标点。

Path path = new Path();

if (!isReady()) {
    return;
} 
else if (routeList != null && nodeList != null) {
    if (!routeList.isEmpty() && !nodeList.isEmpty()) {
        // draw route
        for (int i = 0; i < routeList.size() - 1; i++) {
            PointF goal3 = new PointF(nodeList.get(routeList.get(i)).x, 
                nodeList.get(routeList.get(i)).y);
            PointF goal4 = new PointF(nodeList.get(routeList.get(i + 1)).x, 
                nodeList.get(routeList.get(i + 1)).y);

            sourceToViewCoord(goal3, vPin5);
            sourceToViewCoord(goal4, vPin6);
            path.moveTo(vPin5.x, vPin5.y);
            path.lineTo(vPin6.x, vPin6.y);

            //Draw path on canvas certain coordinate points
            canvas.drawPath(path, paint);
        }
        PointF goal1 = new PointF(nodeList.get(routeList.get(0)).x,
            nodeList.get(routeList.get(0)).y);

        sourceToViewCoord(goal1, vPin3);
        float vX1 = vPin3.x - (location_img.getWidth() / 2);
        float vY1 = vPin3.y - location_img.getHeight() / 2;

        //Draw marker certain coordinate point
        canvas.drawBitmap(location_img, vX1, vY1, paint);

        PointF goal2 = new PointF(nodeList.get(
            routeList.get(routeList.size() - 1)).x, 
            nodeList.get(routeList.get(routeList.size() - 1)).y
        );

        sourceToViewCoord(goal2, vPin4);
        float vX2 = vPin4.x - (pin_red.getWidth() / 2);
        float vY2 = vPin4.y - pin_red.getHeight();

        // Draw bitmap on canvas certain coordinate points
        canvas.drawBitmap(pin_red, vX2, vY2, paint);
    }
}

Answer 1

save和restore方法仅存储转换矩阵和画布的剪辑区域（See the doc）。您无法从画布中删除像素，只需在其上绘制。如果您在图像顶部添加了路径，则应进行仅绘制图像的调用。

请注意，只要您不重新加载或重新创建位图，这在性能上并不是一件大事。

Answer 2

您可以在另一个画布上绘制路径（位图），并且只根据您在图像画布上的愿望绘制路径位图。正如Basile Perrenoud所说，重要的是不要在绘图期间分配路径Bitmap。你可以，例如在类instanciation期间创建它，并在每次重绘时重复使用它。

如何在不刷新和更改图片的情况下从画布中删除路径和标记？

2 个答案: