变焦时覆盖行为 [英] Overlay behavior when zooming

问题描述

我有重叠的麻烦。我画一个多边形叠加在地图上，但是，当我放大或缩小，边缘不再与在那里我希望他们保持一致。我该如何解决这个问题？

I am having trouble with overlays. I have drawn a polygon overlay on the map, however, when I zoom in or out, the edges no longer align with where I want them to. How can I fix this?

下面是什么样子，当我启动应用程序（它涵盖了整个停车场完全）：
正确

Here is what it looks like when I start the app (it covers the whole parking lot perfectly): Correct

下面是什么样子，当我缩小（边缘不再行了停车场叠加看起来比停车场大一点。）：
缩小

Here is what it looks like when I zoom out (edges no longer line up with parking lot. The overlay looks a bit bigger than the parking lot): Zoomed out

此外，它并不当我放大对准好。在这种情况下的覆盖层是停车场小一点。 （对不起，计算器不会让我张贴超过2链接）

Also, it doesn't align well when I zoom in. In this case the overlay is a bit smaller that the parking lot. (Sorry, stackoverflow won't let me post more that 2 links)

这是如何解决这一问题有什么建议？

Any suggestions on how to fix this?

下面是code：

private Projection projection; 
private List<Overlay> mapOverlays;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    MapView mapView = (MapView) findViewById(R.id.mapView); 
    mapView.setBuiltInZoomControls(true);

    MapController mc = mapView.getController();
    mc.setZoom(17); 
    mc.animateTo(new GeoPoint((int)(32.734248*1E6), (int)(-97.113448*1E6)));

    mapOverlays = mapView.getOverlays();        
    projection = mapView.getProjection();
    mapOverlays.add(new MyOverlay());        

    mapView.postInvalidate();
}

@Override
protected boolean isRouteDisplayed() {
    return false;
}

class MyOverlay extends Overlay{

    public MyOverlay(){

    }   

    public void draw(Canvas canvas, MapView mapv, boolean shadow){
        super.draw(canvas, mapv, shadow);

        Paint   mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAlpha(100);

        GeoPoint gP1 = new GeoPoint(32733839,-97112976);
        GeoPoint gP2 = new GeoPoint(32733875, -97113448);
        GeoPoint gP3 = new GeoPoint(32734961,-97113455);
        GeoPoint gP4 = new GeoPoint(32734953, -97112962);

        Point p1 = new Point();
        Point p2 = new Point();
        Point p3 = new Point();
        Point p4 = new Point();
        Path path = new Path();

        projection.toPixels(gP1, p1);
        projection.toPixels(gP2, p2);
        projection.toPixels(gP3, p3);
        projection.toPixels(gP4, p4);

        path.moveTo(p1.x, p1.y);
        path.lineTo(p2.x,p2.y);
        path.lineTo(p3.x,p3.y);
        path.lineTo(p4.x,p4.y);

        canvas.drawPath(path, mPaint);
    }
}

}

推荐答案

每当变焦的变化，投影也随之变化。甚至当您在地图中的大招不改变变焦，投影可能会改变。

Everytime the zoom changes, Projection also changes. Even when you make a large move in the map without changing zoom, projection may change.

要c您需要添加行纠正你的$ C $波纹管：

To correct your code you need to add the line as bellow:

public void draw(Canvas canvas, MapView mapv, boolean shadow){ 
    super.draw(canvas, mapv, shadow); 

    Projection projection = mapv.getProjection();  //Add this line

    Paint   mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); 
    mPaint.setColor(Color.RED); 
    mPaint.setStyle(Paint.Style.FILL); 
    mPaint.setAlpha(100); 

    GeoPoint gP1 = new GeoPoint(32733839,-97112976); 
    GeoPoint gP2 = new GeoPoint(32733875, -97113448); 
    GeoPoint gP3 = new GeoPoint(32734961,-97113455); 
    GeoPoint gP4 = new GeoPoint(32734953, -97112962); 

    Point p1 = new Point(); 
    Point p2 = new Point(); 
    Point p3 = new Point(); 
    Point p4 = new Point(); 
    Path path = new Path(); 

    projection.toPixels(gP1, p1); 
    projection.toPixels(gP2, p2); 
    projection.toPixels(gP3, p3); 
    projection.toPixels(gP4, p4); 

    path.moveTo(p1.x, p1.y); 
    path.lineTo(p2.x,p2.y); 
    path.lineTo(p3.x,p3.y); 
    path.lineTo(p4.x,p4.y); 

    canvas.drawPath(path, mPaint); 
} 

你可以删除的onCreate创建投影（）。

- 编辑 -

改进 - 快速胜

的onDraw（）被调用两次eveytime您移动地图或更改缩放级别，从而使其尽可能这一点很重要。贝娄，你可以找到一些建议：

onDraw() is called twice eveytime you move the map or change zoom level, so it's important to make it as possible. Bellow you can find some suggestions:

private List<Overlay> mapOverlays; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    MapView mapView = (MapView) findViewById(R.id.mapView);  
    mapView.setBuiltInZoomControls(true); 

    MapController mc = mapView.getController(); 
    mc.setZoom(17);  
    mc.animateTo(new GeoPoint((int)(32.734248*1E6), (int)(-97.113448*1E6))); 

    mapOverlays = mapView.getOverlays();         
    mapOverlays.add(new MyOverlay());         

    mapView.postInvalidate(); 
} 

@Override 
protected boolean isRouteDisplayed() { 
    return false; 
} 

class MyOverlay extends Overlay{ 

    //Moved objects that need only one instance to the initialization, to avoid creating a new copy of each every time draw() runs  
    private Paint   mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

    private GeoPoint gP1 = new GeoPoint(32733839,-97112976); 
    private GeoPoint gP2 = new GeoPoint(32733875, -97113448); 
    private GeoPoint gP3 = new GeoPoint(32734961,-97113455); 
    private GeoPoint gP4 = new GeoPoint(32734953, -97112962); 

    private Point p1 = new Point(); 
    private Point p2 = new Point(); 
    private Point p3 = new Point(); 
    private Point p4 = new Point(); 
    private Path path = new Path(); 

    public MyOverlay(){
        //mPaint settings done on class creation, to avoid repeating them on draw() call 
        mPaint.setColor(Color.RED); 
        mPaint.setStyle(Paint.Style.FILL); 
        mPaint.setAlpha(100); 
    }    

    public void draw(Canvas canvas, MapView mapv, boolean shadow){ 
        super.draw(canvas, mapv, shadow); 

        //draw is always called twice, one with shadow equal to true and one to false.
        //This can be used to draw the same image with shadow
        //But you are not using shadows, so you can immediately return half of the calls, and reduce the draw() effort by half
        if(shadow) return;

        Projection projection = mapv.getProjection();

        projection.toPixels(gP1, p1); 
        projection.toPixels(gP2, p2); 
        projection.toPixels(gP3, p3); 
        projection.toPixels(gP4, p4); 

        path.rewind();
        path.moveTo(p1.x,p1.y); 
        path.lineTo(p2.x,p2.y); 
        path.lineTo(p3.x,p3.y); 
        path.lineTo(p4.x,p4.y); 

        canvas.drawPath(path, mPaint); 
    } 
} 

改进 - 更复杂的

我描述波纹管的改进是你当前覆盖一个矫枉过正。它才有意义，当你有真的庞大的路径来绘制。

The improvement I'm describing bellow is a overkill for you current overlay. It only makes sense when you have realy huge paths to draw.

当您移动地图，无需zomming它，用code上述路径将被重新创建，并在不同的地方重绘与地图相一致。但是，你要创建的路径是相同的大小，相同的形状previous之一，只是不同的位置。

When you move the map, without zomming it, with the code above the path will be recreated and redrawn in a different place to be aligned with the map. But the path you are creating is the same size, same shape as the previous one, just in a different position.

您可以用achive同样的结果：

You can achive the same result using:

path.offset(dx, dy);

其中， DX，DY 是你需要移动的路径，使之与地图排列的像素数。当然，你需要跟踪在那里有地图你最后一次偏移的路径，这样就可以抵消的路径，新地图的位置。

where dx, dy is the number of pixels you need to move the path to keep it aligned with the map. Of course, you need to keep track where was the map last time you offset the path, so you can offset the path to the new map position.

如果你有几千点的路径，抵减道路将快大约100倍，然后重绘。

If you have a path with several thousands of points, offseting the path will be about 100 times faster then redrawing it.

您还需要跟踪的缩放级别，因为你仍然需要重建路径缩放变化时。不能使用 getCurrentZoomLevel（）来做到这一点，因为没有汇入作业与缩放动画同步。你需要测试 longitudeSpan（）值的变化，能够有变焦改变动画同步路径创造。

You also need to keep track on zoom level, as you still need to recreate the path when zoom changes. You can't use getCurrentZoomLevel() to do it, as it´s not synchronized with zoom animation. You need to test longitudeSpan() value changes, to be able to have a synchronized path creation with zoom change animation.

我希望这会有所帮助。

问候。

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