我正在使用 SO 上的一个很棒的位置类来通过网络或 gps 获取我的位置。它可以工作并为我提供 Log.i() 输出中的位置，但是，当我尝试将这些变量添加到 textView 时，我得到一个空指针异常。
这是我的紧急课程：
public class EmergencyActivity extends NavigationActivity {
private TextView tvYourLocation;
public String wxUrl;
public String latlon;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//show no back arrow
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.activity_emergency);
LocationResult locationResult = new LocationResult(){
@Override
public void gotLocation(Location location){
//Got the location!
latlon = "Latitude: " + location.getLatitude() + "<br/> Longitude: " + location.getLongitude();
Log.i("URL",latlon);
tvYourLocation = (TextView) findViewById(R.id.todaysReport);
tvYourLocation.setText(Html.fromHtml("<strong>Your current location is: <br/>" + latlon +"</strong>"));
}
};
MyLocation myLocation = new MyLocation();
myLocation.getLocation(this, locationResult);
}
}
我将此类用于 myLocation：
public class MyLocation {
Timer timer1;
LocationManager lm;
LocationResult locationResult;
boolean gps_enabled=false;
boolean network_enabled=false;
public boolean getLocation(Context context, LocationResult result)
{
//I use LocationResult callback class to pass location value from MyLocation to user code.
locationResult=result;
if(lm==null)
lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
//exceptions will be thrown if provider is not permitted.
try{gps_enabled=lm.isProviderEnabled(LocationManager.GPS_PROVIDER);}catch(Exception ex){}
try{network_enabled=lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER);}catch(Exception ex){}
//don't start listeners if no provider is enabled
if(!gps_enabled && !network_enabled)
return false;
if(gps_enabled)
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListenerGps);
if(network_enabled)
lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListenerNetwork);
timer1=new Timer();
timer1.schedule(new GetLastLocation(), 20000);
return true;
}
LocationListener locationListenerGps = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(location);
lm.removeUpdates(this);
lm.removeUpdates(locationListenerNetwork);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
LocationListener locationListenerNetwork = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(location);
lm.removeUpdates(this);
lm.removeUpdates(locationListenerGps);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
class GetLastLocation extends TimerTask {
@Override
public void run() {
lm.removeUpdates(locationListenerGps);
lm.removeUpdates(locationListenerNetwork);
Location net_loc=null, gps_loc=null;
if(gps_enabled)
gps_loc=lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(network_enabled)
net_loc=lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
//if there are both values use the latest one
if(gps_loc!=null && net_loc!=null){
if(gps_loc.getTime()>net_loc.getTime())
locationResult.gotLocation(gps_loc);
else
locationResult.gotLocation(net_loc);
return;
}
if(gps_loc!=null){
locationResult.gotLocation(gps_loc);
return;
}
if(net_loc!=null){
locationResult.gotLocation(net_loc);
return;
}
locationResult.gotLocation(null);
}
}
public static abstract class LocationResult{
public abstract void gotLocation(Location location);
}
}
...在这里找到：在 Android 上获取用户当前位置的最简单、最可靠的方法是什么？
我如何找到这个 Null？
这是我的日志输出：
12-06 22:00:52.151: E/AndroidRuntime(19936): FATAL EXCEPTION: main
12-06 22:00:52.151: E/AndroidRuntime(19936): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.backcountryskiers.avalanche.conditions/com.backcountryskiers.avalanche.conditions.EmergencyActivity}: java.lang.NullPointerException
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.os.Handler.dispatchMessage(Handler.java:99)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.os.Looper.loop(Looper.java:137)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread.main(ActivityThread.java:5039)
12-06 22:00:52.151: E/AndroidRuntime(19936): at java.lang.reflect.Method.invokeNative(Native Method)
12-06 22:00:52.151: E/AndroidRuntime(19936): at java.lang.reflect.Method.invoke(Method.java:511)
12-06 22:00:52.151: E/AndroidRuntime(19936): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-06 22:00:52.151: E/AndroidRuntime(19936): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-06 22:00:52.151: E/AndroidRuntime(19936): at dalvik.system.NativeStart.main(Native Method)
12-06 22:00:52.151: E/AndroidRuntime(19936): Caused by: java.lang.NullPointerException
12-06 22:00:52.151: E/AndroidRuntime(19936): at com.backcountryskiers.avalanche.conditions.EmergencyActivity.onCreate(EmergencyActivity.java:43)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.Activity.performCreate(Activity.java:5104)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-06 22:00:52.151: E/AndroidRuntime(19936): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-06 22:00:52.151: E/AndroidRuntime(19936): ... 11 more