谷歌地图查看＆QUOT;而在Android的例子＆QUOT语境的问题; [英] Context problem in Android example "Google Map View"

问题描述

我已经试过落实谷歌地图视图教程对Android开发者网站，但我一直试图显示一个AlertDialog当我点击的叠加图像时遇到了一个问题。问题是，mContext调用时为空

I've tried to implement the Google Map View tutorial on the Android developer site, but I keep running into a problem when trying to display an AlertDialog when I click on the overlay image. The problem is that mContext is null when calling

AlertDialog.Builder dialog = new AlertDialog.Builder(mContext);

在HelloItemizedOverlay的方法的onTap由于构造

in HelloItemizedOverlay's onTap method because the constructor

public HelloItemizedOverlay(Drawable defaultMarker, Context context) {
    super(boundCenterBottom(defaultMarker));
    mContext = context;
}

永远不会被调用（即我可以告诉），它初始化mContext。当我更换

is never called (that I can tell) which initializes mContext. When I replace

HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable);

与

HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable, 
                this.getApplicationContext());

在HelloGoogleMaps的，以初始化上下文onCreate方法，我得到一个异常

in HelloGoogleMaps's onCreate method in order to initialize the context, I get an exception

android.view.WindowManager $ BadTokenException：无法添加窗口 - 令牌null不是一个应用程序

android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application

当我尝试显示AlertDialog像这样：

when I try to display the AlertDialog like so:

dialog.show();

我认为这个教程已成功成千上万的人实现的，所以我在为什么没有其他人遇到了这个问题茫然......有我错过了本教程的一个重要步骤？

I assume this tutorial has been successfully implemented by thousands of people, so I'm at a loss why no one else has run into this problem... have I missed an important step from the tutorial?

推荐答案

我想你需要图形页面的上下文传递给HelloItemizedOverlay构造像这样：

I think you need to pass mapView's context to the HelloItemizedOverlay constructor like so:

HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable, mapView.getContext());

很显然本教程的code样品中的错误。小错误，这样的疏漏都没有在参考文档屡见不鲜，尤其是对于大型项目像Android一样。

There is clearly an error in the tutorial's code sample. Small errors and omissions like this are not uncommon within reference documentation, especially for a large project like Android.

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