Android Mapview 平移和缩放太慢

Question

我开发了一个 GPS 应用程序，我在其中记录用户根并显示它在 map 上......但是查看我的路线时在 map 上平移非常慢， map 至少需要4或5秒才能响应手指轻扫……

我已经覆盖了 onDraw() 方法并绘制线条以显示路线......有没有更好的方法来做到这一点，以便平移成为比 "MyTracks" 更快......

谢谢大家......Pratap S.

Answer 1

我不得不做 something similar .我的尝试目前在 onDraw 中执行以下操作(为了可读性而简化 - 错误处理等被删除):

if ((bmap == null) || (lastZoom != mapv.getLatitudeSpan()))
{
    // bitmap is null - so we haven't previously drawn the path, OR
    //  the map has been zoomed in/out, so we're gonna re-draw it anyway
    //    (alternatively, I could have tried scaling the bitmap... might
    //     be worth investigating if that is more efficient)

    Projection proj = mapv.getProjection();

    // store zoom level for comparing in the next onDraw
    lastZoom = mapv.getLatitudeSpan();

    // draw a path of all of the points in my route
    GeoPoint start = routePoints.get(0);
    Point startPt = new Point();            
    proj.toPixels(start, startPt);

    Path path = new Path();
    path.moveTo(startPt.x, startPt.y);

    Point nxtPt;

    for (GeoPoint nextPoint : routePoints) 
    {
        nxtPt = new Point();
        proj.toPixels(nextPoint, nxtPt);
        path.lineTo(nxtPt.x, nxtPt.y);
    }

    // create a new bitmap, the size of the map view
    bmap = Bitmap.createBitmap(mapv.getWidth(), mapv.getHeight(), Bitmap.Config.ARGB_8888);

    // create an off-screen canvas to prepare new bitmap, and draw path on to it
    Canvas offscreencanvas = new Canvas(bmap);
    offscreencanvas.drawPath(path, mPaint);

    // draw the bitmap of the path onto my map view's canvas
    canvas.drawBitmap(bmap, 0, 0, null);

    // make a note of where we put the bitmap, so we know how much we 
    //  we need to move it by if the user pans the map
    mapStartPosition = proj.fromPixels(0, 0);
}
else
{
    // as we're in onDraw, we think the user has panned/moved the map
    //  if we're in here, the zoom level hasn't changed, and
    //   we've already got a bitmap with a drawing of the route path

    Projection proj = mapv.getProjection();

    // where has the mapview been panned to?
    Point offsetPt = new Point();
    proj.toPixels(mapStartPosition, offsetPt);

    // draw the bitmap in the new correct location
    canvas.drawBitmap(bmap, offsetPt.x, offsetPt.y, null);
}

它还不完美....例如，路径在缩放后立即结束在错误的位置 - 一旦用户开始平移就被移动到正确的位置。

但这是一个开始 - 并且比在每次 onDraw 调用时重新绘制路径更有效

希望这对您有所帮助!