Question

我无法将主要活动OnCreate方法中的任务卸载到另一个类来完成繁重的工作。

当我尝试从非Activity类调用getSystemService时会抛出异常。

非常感谢任何帮助：）

lmt.java：

package com.atClass.lmt;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import android.location.Location;

public class lmt extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        fyl lfyl = new fyl();
        Location location = lfyl.getLocation();
        String latLongString = lfyl.updateWithNewLocation(location);

        TextView myLocationText = (TextView)findViewById(R.id.myLocationText);
        myLocationText.setText("Your current position is:\n" + latLongString);
    }
}

fyl.java

package com.atClass.lmt;

import android.app.Activity;
import android.os.Bundle;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;
import android.content.Context;

public class fyl {
    public Location getLocation(){
        LocationManager locationManager;
        String context = Context.LOCATION_SERVICE;
        locationManager = (LocationManager)getSystemService(context);

        String provider = LocationManager.GPS_PROVIDER;
        Location location = locationManager.getLastKnownLocation(provider);

        return location;
    }

    public String updateWithNewLocation(Location location) {
        String latLongString;

        if (location != null){
            double lat = location.getLatitude();
            double lng = location.getLongitude();
            latLongString = "Lat:" + lat + "\nLong:" + lng;
        }else{
            latLongString = "No Location";
        }

        return latLongString;
    }
}

Answer 1

您需要将您的上下文传递给您的fyl类..
一种解决方案是为fyl类创建这样的构造函数：

public class fyl {
 Context mContext;
 public fyl(Context mContext) {
       this.mContext = mContext;
 }

 public Location getLocation() {
       --
       locationManager = (LocationManager)mContext.getSystemService(context);

       --
 }
}

因此，在您的activity类中，在onCreate函数中创建fyl的对象，如下所示：

package com.atClass.lmt;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import android.location.Location;

public class lmt extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        fyl lfyl = new fyl(this); //Here the context is passing 

        Location location = lfyl.getLocation();
        String latLongString = lfyl.updateWithNewLocation(location);

        TextView myLocationText = (TextView)findViewById(R.id.myLocationText);
        myLocationText.setText("Your current position is:\n" + latLongString);
    }
}

Answer 2

你可以这样做：

getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);

Answer 3

我解决这个问题的一种方法是为实例创建一个静态类。我在AS3中经常使用它我在android开发方面也很适合我。

<强> Config.java

public final class Config {
    public static MyApp context = null;
}

<强> MyApp.java

public class MyApp extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Config.context = this;
    }
    ...
}

然后，您可以访问上下文或使用Config.context

LocationManager locationManager;
String context = Context.LOCATION_SERVICE;
locationManager = Config.context.getSystemService(context);

Answer 4

我不知道这是否会有所帮助，但我这样做了：

LocationManager locationManager  = (LocationManager) context.getSystemService(context.LOCATION_SERVICE);

Answer 5

对于某些非活动类，例如Worker，您已经在公共构造函数中获得了Context对象。

Worker(Context context, WorkerParameters workerParams)

您可以使用它，例如将其保存到类中的私有Context变量中（例如mContext），然后例如

mContext.getSystenService(Context.ACTIVITY_SERVICE)

Answer 6

使用此在活动中：

private Context context = this;

........
if(Utils.isInternetAvailable(context){
Utils.showToast(context, "toast");
}
..........

在实用程序中：

public class Utils {

    public static boolean isInternetAvailable(Context context) {
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        return cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected();
    }

}

Answer 7

如果你想把它放在一个片段中，这可以在 kotlin 中工作：

requireActivity().getSystemService(LOCATION_SERVICE) as LocationManager

Answer 8

(LocationManager) ((lmt) new Activity()).getSystemService(context);

试试这段代码。只有在调用此行代码之前已启动活动时，此方法才有效。因为活动必须创建并且正在运行。

如何在非活动类（LocationManager）中使用getSystemService？

8 个答案: