Android LocationListener返回空值

Question

public class MainActivity extends Activity implements LocationListener {
    TextView tv;
    TextView tv2;
    TextView tv3;
    LocationListener locationListener;
    static final String tag="********MAIN********";
    LocationManager lm;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lm = (LocationManager) getSystemService(LOCATION_SERVICE);
    }
    @Override
    protected void onResume() {
        super.onResume();
        lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);
    }
    @Override
    public void onLocationChanged(Location location) {
        Log.i(tag,"Location Changed Method Called");
        String lat= String.valueOf(location.getLatitude());
        String log= String.valueOf(location.getLongitude());
        tv.setText(lat+ " " + log);
    }
    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }
    @Override
    public void onProviderEnabled(String provider) {
    }
    @Override
    public void onProviderDisabled(String provider) {
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="p2p.boysjoys.com.alpha" >

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >


        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

这一行是：

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);

我在Phone和Emulator上尝试了GPS和Network，但仍然给出相同的错误java.lang.IllegalArgumentException:listener==null

Answer 1

更改：

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);

有了这个：

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,this);

您的类已经实现了LocationListener。就用吧。（但是，在代码中，您尝试使用LocationListener，而不对其进行初始化）