我有两节课。
MainActivity：
package ytu.ytu1;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.provider.Settings;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private Button gpsBtn;
private TextView gpsTxt;
private LocationManager locMngr;
private LocationListener locLstnr;
GPSTracker gps;
double lot,lat;
String txt;
private static final long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 1; // in Meters
private static final long MINIMUM_TIME_BETWEEN_UPDATES = 1000; // in Milliseconds
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lat=gps.getLocation().getLongitude();
lot=gps.getLocation().getLatitude();
txt="longti "+lat + "latit " +lot;
gpsTxt = (TextView) findViewById(R.id.gpsTxt);
gpsTxt.setText("Coordinates: ");
gpsTxt.append(txt);
Toast.makeText(MainActivity.this,txt,
Toast.LENGTH_LONG).show();
}}
GPSTracker.java来自这里 http://pastie.org/9300205
只有权限被更改，因为我在Android kitkat平板电脑上使用它。
package ytu.ytu1;
/**
* Created by mia on 11/28/2015.
*/
import android.Manifest;
import android.annotation.TargetApi;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
private TextView txt;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 5000; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSTracker(Context context) {
this.mContext = context;
getLocation();
}
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public void StoprequestUpdates() {
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_FINE_LOCATION) !=
PackageManager.PERMISSION_GRANTED && ContextCompat.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.
if (isGPSEnabled) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
if (isNetworkEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
return;
} else {
}
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
// if GPS Enabled get lat/long using GPS Services
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) !=
PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) !=
PackageManager.PERMISSION_GRANTED) {
if (isGPSEnabled) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
if (isNetworkEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
/**
* Stop using GPS listener Calling this function will stop using GPS in your
* app
* */
public void stopUsingGPS() {
if (locationManager != null) {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) !=
PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION) !=
PackageManager.PERMISSION_GRANTED) {
locationManager.removeUpdates(GPSTracker.this);return;}
}
}
/**
* Function to get latitude
* */
public double getLatitude() {
if (location != null) {
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude() {
if (location != null) {
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
*
* @return boolean
*
*
*
*
* */
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog On pressing Settings button will
* lauch Settings Options
* */
public void showSettingsAlert() {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog
.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
@Override
public void onLocationChanged(Location location) {
if (location != null) {
this.location = location;
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}
我甚至无法调试，一旦启动，它就会崩溃而不显示任何视图。
logcat的：
11-28 16:51:19.541 9413-9413/? D/dalvikvm: Late-enabling CheckJNI
11-28 16:51:19.591 9413-9413/? D/ActivityThread: handleBindApplication:ytu.ytu1
11-28 16:51:19.621 9413-9413/ytu.ytu1 W/ApplicationPackageManager: getCSCPackageItemText()
11-28 16:51:19.631 9413-9413/ytu.ytu1 D/DisplayManager: DisplayManager()
11-28 16:51:19.641 9413-9413/ytu.ytu1 W/dalvikvm: VFY: unable to find class referenced in signature (Landroid/view/SearchEvent;)
11-28 16:51:19.641 9413-9413/ytu.ytu1 I/dalvikvm: Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onSearchRequested
11-28 16:51:19.641 9413-9413/ytu.ytu1 W/dalvikvm: VFY: unable to resolve interface method 17904: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z
11-28 16:51:19.641 9413-9413/ytu.ytu1 D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
11-28 16:51:19.641 9413-9413/ytu.ytu1 I/dalvikvm: Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onWindowStartingActionMode
11-28 16:51:19.641 9413-9413/ytu.ytu1 W/dalvikvm: VFY: unable to resolve interface method 17908: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode;
11-28 16:51:19.641 9413-9413/ytu.ytu1 D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
11-28 16:51:19.661 9413-9413/ytu.ytu1 D/AndroidRuntime: Shutting down VM
11-28 16:51:19.661 9413-9413/ytu.ytu1 W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x416adbc0)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: FATAL EXCEPTION: main
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: Process: ytu.ytu1, PID: 9413
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{ytu.ytu1/ytu.ytu1.MainActivity}: java.lang.NullPointerException
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2429)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2493)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.access$800(ActivityThread.java:166)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:102)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.os.Looper.loop(Looper.java:136)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5584)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:515)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: Caused by: java.lang.NullPointerException
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at ytu.ytu1.MainActivity.onCreate(MainActivity.java:44)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.Activity.performCreate(Activity.java:5447)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2393)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2493)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.access$800(ActivityThread.java:166)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:102)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.os.Looper.loop(Looper.java:136)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5584)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:515)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
11-28 16:51:19.661 9413-9413/ytu.ytu1 E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
我在android studio上使用，我没有改变原始代码。我不明白为什么它不会开始。
答案 0 :(得分：0)
尝试这样的事情：
GPSTracker gps = new GPSTracker(this);
还请查看本教程：http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial/