【发布时间】：2016-06-08 06:12:48
【问题描述】：
我在将 Location 从服务发送到自定义 BroadcastReceiver 时遇到问题。
这是我的 BroadcastReceiver.cs
[BroadcastReceiver]
class MyBroadcastReceiver : BroadcastReceiver
{
public static readonly string GRID_STARTED = "GRID_STARTED";
public event EventHandler<OnLocationChangedEventArgs> mOnLocationChanged;
private Location location;
public override void OnReceive(Context context, Intent intent)
{
if (intent.Action == GRID_STARTED)
{
Toast.MakeText(context, "Grid Started", ToastLength.Short).Show();
//location = JsonConvert.DeserializeObject<Location>(intent.GetStringExtra("location"));
//mOnLocationChanged.Invoke(this, new OnLocationChangedEventArgs(location));
}
}
}
如果我取消注释上面代码中的两行，我的应用程序会突然停止。我无法告诉您错误是什么，因为在开发 Xamarin 应用程序时，调试因内部错误而停止（我在 Xamarin 论坛上读到过它，但找不到时间来处理它）。
这是我在服务中所做的：
private void BroadcastStarted(Location location)
{
Intent BroadcastIntent = new Intent(this, typeof(MyBroadcastReceiver));
BroadcastIntent.PutExtra("location",JsonConvert.SerializeObject(location));
BroadcastIntent.SetAction(MyBroadcastReceiver.GRID_STARTED);
BroadcastIntent.AddCategory(Intent.CategoryDefault);
SendBroadcast(BroadcastIntent);
}
我正在使用 Newtonsoft.Json 发送一个对象。 任何帮助将不胜感激。
更新：
好的，不知何故我设法揭示了错误：
找不到用于类型的构造函数 安卓.位置.位置。一个类应该有一个默认值 构造函数，带参数的构造函数或标记的构造函数 带有 JsonConstructor 属性。
更新：
整个服务代码：
using Newtonsoft.Json;
namespace GoogleMaps
{
public class OnLocationChangedEventArgs
{
Location location;
public Location Location
{
get { return location; }
set { location = value; }
}
public OnLocationChangedEventArgs(Location location)
{
this.location = location;
}
}
[Service]
class MyService : Service
{
private LocationManager locationManager = null;
public MyService()
{
}
private class MyLocationListener : Java.Lang.Object,ILocationListener
{
Location mLastLocation;
public event EventHandler<OnLocationChangedEventArgs> onLoc;
public MyLocationListener(String provider)
{
mLastLocation = new Location(provider);
}
public void OnLocationChanged(Location location)
{
try
{
mLastLocation.Set(location);
onLoc.Invoke(this, new OnLocationChangedEventArgs(mLastLocation));
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
public void OnProviderDisabled(string provider)
{
}
public void OnProviderEnabled(string provider)
{
}
public void OnStatusChanged(string provider, [GeneratedEnum] Availability status, Bundle extras)
{
}
}
private MyLocationListener locationListener = new MyLocationListener("network");
public override IBinder OnBind(Intent intent)
{
return null;
}
private void BroadcastStarted(Location location)
{
Intent BroadcastIntent = new Intent(this, typeof(MyBroadcastReceiver));
BroadcastIntent.PutExtra("location",JsonConvert.SerializeObject(location));
BroadcastIntent.SetAction(MyBroadcastReceiver.GRID_STARTED);
BroadcastIntent.AddCategory(Intent.CategoryDefault);
SendBroadcast(BroadcastIntent);
}
[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
return StartCommandResult.Sticky;
}
public override void OnCreate()
{
try
{
base.OnCreate();
InitializeLocationManager();
locationManager.RequestLocationUpdates(LocationManager.NetworkProvider, 0, 0, locationListener);
locationListener.onLoc += MyService_onLoc;
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
private void MyService_onLoc(object sender, OnLocationChangedEventArgs e)
{
BroadcastStarted(e.Location);
}
public override void OnDestroy()
{
base.OnDestroy();
locationManager.RemoveUpdates(locationListener);
}
private void InitializeLocationManager()
{
if (locationManager == null)
{
locationManager = (LocationManager)GetSystemService(LocationService);
}
}
}
}
更新：
这是我在第 6 条评论中所说的：
public override void OnReceive(Context context, Intent intent)
{
if (intent.Action == GRID_STARTED)
{
try
{
Toast.MakeText(context, "Grid Started", ToastLength.Short).Show();
a = new LatLng(intent.GetDoubleExtra("latitude",0),intent.GetDoubleExtra("longitude",0));
mOnLocationChanged.Invoke(this, new OnLatLngChangedEventArgs(a)); // NULL EXCEPTION LINE
}
catch (Exception ex)
{
Toast.MakeText(context, ex.Message, ToastLength.Short).Show();
}
}
}
为什么事件处理程序 mOnLocationChanged 等于 null？ 和服务的一部分：
private void BroadcastStarted(Location location)
{
Intent BroadcastIntent = new Intent(this, typeof(MyBroadcastReceiver));
BroadcastIntent.PutExtra("latitude",location.Latitude);
BroadcastIntent.PutExtra("longitude", location.Longitude);
BroadcastIntent.SetAction(MyBroadcastReceiver.GRID_STARTED);
BroadcastIntent.AddCategory(Intent.CategoryDefault);
SendBroadcast(BroadcastIntent);
}
【问题讨论】：
-
服务中位置在哪里初始化？
-
我在 LocationListener 中获取位置，然后通过 eventHandler 将其传递给服务
-
所以 LocationListener 将“位置”对象发送到 BroadcastStarted(Here) ？可以发一些代码吗？
-
我已经更新了我的问题
-
我认为这仅在位置更改时才有效，否则 mLastLocation 中将没有任何值，因为它仅在 onLocationChange 事件触发时设置。尝试通过在设备或模拟器上测试来模拟位置变化。
标签： c# android service xamarin broadcastreceiver