Java 致命异常：主Android

嗨，我是android开发的新手。我试图使用GPS获取用户坐标，我得到的错误是致命异常：主Android

这是我的密码

package lk.adspace.finetech;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

public class Main extends Activity implements LocationListener {

    TextView viewlocation;

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

        LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L,1.0f, this);
        boolean isGPS = locationManager.isProviderEnabled (LocationManager.GPS_PROVIDER);

        if (isGPS){

        }else{
            startActivityForResult(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);
        }

        String locationProvider = LocationManager.GPS_PROVIDER;
        locationManager.requestLocationUpdates(locationProvider, 400, 1, this);

        // Location loc =   locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        Location loc =   locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        viewlocation = (TextView) findViewById(R.id.location);
        viewlocation.setText("My Current location \n Latitude = "+ loc.getLatitude()+" \n Longitude = "+ loc.getLongitude());
    }

    ...
}

这就是我得到的错误

08-20 12:08:37.436: E/AndroidRuntime(25888): FATAL EXCEPTION: main
08-20 12:08:37.436: E/AndroidRuntime(25888): java.lang.RuntimeException: Unable to start activity ComponentInfo{lk.adspace.finetech/lk.adspace.finetech.Main}: java.lang.NullPointerException
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread.access$600(ActivityThread.java:162)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.os.Handler.dispatchMessage(Handler.java:107)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.os.Looper.loop(Looper.java:194)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread.main(ActivityThread.java:5371)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at java.lang.reflect.Method.invokeNative(Native Method)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at java.lang.reflect.Method.invoke(Method.java:525)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at dalvik.system.NativeStart.main(Native Method)
08-20 12:08:37.436: E/AndroidRuntime(25888): Caused by: java.lang.NullPointerException
08-20 12:08:37.436: E/AndroidRuntime(25888):    at lk.adspace.finetech.Main.onCreate(Main.java:68)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.Activity.performCreate(Activity.java:5122)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
08-20 12:08:37.436: E/AndroidRuntime(25888):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
08-20 12:08:37.436: E/AndroidRuntime(25888):    ... 11 more

---

有人能帮我解决这个问题吗。tnx.

第68行存在空指针异常

我认为下面的loc返回为null。请查收

Location loc =   locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

---

访问loc.getLatitude（）时，其引发异常。您可以添加空检查或从其他提供程序获取位置。另外，检查GPS提供商当前是否已禁用。

我认为您应该检查loc是否为空

     if (loc != null)     {
     viewlocation = (TextView) findViewById(R.id.location);
     viewlocation.setText("My Current location \n Latitude = "+ loc.getLatitude()+" \n       Longitude = "+ loc.getLongitude());
     }

---

您正在检查GPS是否作为布尔值启用

isGPS

。将代码移动到块内。当GPS提供程序未通过设置启用时，可能会引发异常。您的代码可能如下所示：

    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L,1.0f, this);
    boolean isGPS = locationManager.isProviderEnabled (LocationManager.GPS_PROVIDER);

    if (isGPS){  
    // -------- IF GPS IS ENABLED, GET COORDINATES AND DISPLAY TO USER ------

        String locationProvider = LocationManager.GPS_PROVIDER;
        locationManager.requestLocationUpdates(locationProvider, 400, 1, this);

        Location loc =   locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if (loc != null)     // <---- This line can be included to avoid null pointer exception in case you are not able to get the coordinates.
        {
            viewlocation = (TextView) findViewById(R.id.location);
             viewlocation.setText("My Current location \n Latitude = "+ loc.getLatitude()+" \n Longitude = "+ loc.getLongitude());
       }

    }else{

    // --------IF GPS NOT ENABLED, THEN MOVE TO SETTINGS SCREEN TO HELP USER TO ENABLE GPS.
        startActivityForResult(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);
    }

LocationManager LocationManager=（LocationManager）getSystemService（LOCATION\u服务）；
locationManager.RequestLocationUpdate（locationManager.GPS_提供程序，1000L，1.0f，此）；
布尔值isGPS=locationManager.isProviderEnabled（locationManager.GPS\U提供程序）；
如果（isGPS）{
//-----如果启用了GPS，则获取坐标并向用户显示------
字符串locationProvider=LocationManager.GPS\u PROVIDER；
locationManager.RequestLocationUpdate（locationProvider，400，1，this）；
Location loc=locationManager.getLastKnownLocation（locationManager.GPS\U提供程序）；
if（loc！=null）//签出
getLastKnownLocation
可以返回
Main.onCreate（Main.java:68）
行中的null值吗？它在onCreate方法的第68行返回NullPointerException。代码的哪一部分是第68行？您可能需要阅读此内容
    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L,1.0f, this);
    boolean isGPS = locationManager.isProviderEnabled (LocationManager.GPS_PROVIDER);

    if (isGPS){  
    // -------- IF GPS IS ENABLED, GET COORDINATES AND DISPLAY TO USER ------

        String locationProvider = LocationManager.GPS_PROVIDER;
        locationManager.requestLocationUpdates(locationProvider, 400, 1, this);

        Location loc =   locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if (loc != null)     // <---- This line can be included to avoid null pointer exception in case you are not able to get the coordinates.
        {
            viewlocation = (TextView) findViewById(R.id.location);
             viewlocation.setText("My Current location \n Latitude = "+ loc.getLatitude()+" \n Longitude = "+ loc.getLongitude());
       }

    }else{

    // --------IF GPS NOT ENABLED, THEN MOVE TO SETTINGS SCREEN TO HELP USER TO ENABLE GPS.
        startActivityForResult(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);
    }