Android: LocationManager 在另一个 class

Question

感谢您的帮助，到目前为止，我设法让该应用正常运行！现在我想将一些代码与其他代码分开，但我不断收到一些错误...

错误：

09-23 17:06:20.129    9324-9324/com.example.stefano.aiutomamma01 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.stefano.aiutomamma01, PID: 9324
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.stefano.aiutomamma01/com.example.stefano.aiutomamma01.MainActivity}: java.lang.IllegalStateException: System services not available to Activities before onCreate()
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
     Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
            at android.app.Activity.getSystemService(Activity.java:5253)
            at com.example.stefano.aiutomamma01.GPS.<init>(GPS.java:20)
            at com.example.stefano.aiutomamma01.MainActivity.onCreate(MainActivity.java:25)
            at android.app.Activity.performCreate(Activity.java:6237)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

class 主活动

package com.example.stefano.aiutomamma01;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

//    //GPS
//    private LocationManager locationManager;

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

//        //GPS
//        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
//        //CATCHED
//        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
//                && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
//            // TODO: Consider calling
//            //    public void requestPermissions(@NonNull String[] permissions, int requestCode)
//            // here to request the missing permissions, and then overriding
//            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
//            //                                          int[] grantResults)
//            // to handle the case where the user grants the permission. See the documentation
//            // for Activity#requestPermissions for more details.
//            return;
//        }
//        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


//    //GPS
//    @Override
//    public void onLocationChanged(Location location) {
//        String str = "Latitude: " + location.getLatitude() + " Longitude: " + location.getLongitude();
//        Toast.makeText(getBaseContext(), str, Toast.LENGTH_LONG).show();
//    }
//
//    //GPS
//    @Override
//    public void onStatusChanged(String provider, int status, Bundle extras) {
//
//
//    }
//
//    //GPS
//    @Override
//    public void onProviderEnabled(String provider) {
//
//    }
//
//    //GPS
//    @Override
//    public void onProviderDisabled(String provider) {
//
//    }

}

class GPS

package com.example.stefano.aiutomamma01;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;

public class GPS extends AppCompatActivity implements LocationListener {

    private LocationManager locationManager;

    public GPS() {
        //GPS
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        //CATCHED
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    public void requestPermissions(@NonNull String[] permissions, int requestCode)
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for Activity#requestPermissions for more details.
            return;
        }
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);

    }


    //GPS
    @Override
    public void onLocationChanged(Location location) {
        String str = "Latitude: " + location.getLatitude() + " Longitude: " + location.getLongitude();
        Toast.makeText(getBaseContext(), str, Toast.LENGTH_LONG).show();

    }

    //GPS
    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    //GPS
    @Override
    public void onProviderEnabled(String provider) {

    }

    //GPS
    @Override
    public void onProviderDisabled(String provider) {

    }

}

实际上我只是分离了一些代码，但我一直收到错误。我尝试了一些出路，但它仍然无法正常工作......我忘记了一些非常小的事情。你能帮帮我吗？

Answer 1

因为你只是分离关注点，你应该将你的主要Activity作为构造函数参数传递给你的新class。

试试这个：

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new GPS(this);
}

现在使用您的 MainActivity 上下文，在 GPS class.

内

已添加

尽管您的 GPS 从 AppCompatActivity 扩展而来，但它不是 Activity。 Activity 需要由 Android 管理。

在我看来，您可以使用 MainActivity 上下文，并让 GPS class 作为一个简单的 POJO。在您的 GPS class 中，您应该添加一个接收 Activity.

的构造函数

private Activity mainActivity;

public GPS(Activity activity){
   this.mainActivity =  activity;
   locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
}

这样做，MainClass 会扩展 LocationService。您只需将调用委托给 GPS class 方法。

Android: LocationManager 在另一个 class

Android: LocationManager in another class

java

gps

android

class