java - GPS应用程序崩溃

Question

我必须编写一个应用程序来执行多项操作，包括在输入正确的用户名和密码时记录用户的 GPS 位置。我只想要那一刻的纬度和经度，不需要重复检查或任何类似性质的东西。我想我找到了与我正在寻找的类似的东西:

How to call to get a single gps fix when ever i want android?

但是，Eclipse 不喜欢这个上下文，因为我还没有初始化它。这是整个代码部分:

Context context = getBaseContext();
LocationManager locMan = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
Log.i(getClass().getSimpleName(),"Location Manager called");
Location loc = locMan.getLastKnownLocation(LocationManager.GPS_PROVIDER);
Log.i(getClass().getSimpleName(),"Last known location received");
Double latitude = loc.getLatitude();
Log.i(getClass().getSimpleName(),"Latitude:"+latitude);
Double longitude = loc.getLongitude();
Log.i(getClass().getSimpleName(),"Longitude:"+longitude);
Toast.makeText(context, latitude+","+longitude, Toast.LENGTH_LONG).show();

对于 list 中的权限:

<uses-permission android:name="com.foxcatch.code.insecure.LOCATION_FINDER" /> 
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

但是，当我尝试访问纬度和经度并将它们分配给 double 时，这会崩溃:

Double latitude = loc.getLatitude();
Double longitude = loc.getLongitude();

这是 LogCat 错误条目，它有点超出我的理解范围:

04-28 18:00:39.346: E/AndroidRuntime(32548): FATAL EXCEPTION: main 04-28 18:00:39.346: E/AndroidRuntime(32548): Process: com.rps.personaldata, PID: 32548 04-28 18:00:39.346: E/AndroidRuntime(32548): java.lang.NullPointerException 04-28 18:00:39.346: E/AndroidRuntime(32548): at com.rps.personaldata.MainActivity$1.onClick(MainActivity.java:58) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.view.View.performClick(View.java:4445) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.view.View$PerformClick.run(View.java:18429) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.os.Handler.handleCallback(Handler.java:733) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.os.Handler.dispatchMessage(Handler.java:95) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.os.Looper.loop(Looper.java:136) 04-28 18:00:39.346: E/AndroidRuntime(32548): at android.app.ActivityThread.main(ActivityThread.java:5081) 04-28 18:00:39.346: E/AndroidRuntime(32548): at java.lang.reflect.Method.invokeNative(Native Method) 04-28 18:00:39.346: E/AndroidRuntime(32548): at java.lang.reflect.Method.invoke(Method.java:515) 04-28 18:00:39.346: E/AndroidRuntime(32548): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781) 04-28 18:00:39.346: E/AndroidRuntime(32548): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 04-28 18:00:39.346: E/AndroidRuntime(32548): at dalvik.system.NativeStart.main(Native Method)

我是 Android 新手，我只是想弄清楚这一切。感谢您的帮助。

Answer 1

为什么要获取BaseContext..只需直接调用getSystemService

更改此:

LocationManager locMan = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);

致:

LocationManager locMan = (LocationManager)getSystemService(Context.LOCATION_SERVICE);