Java 如何避免位置服务的NullPointerException?
在我的应用程序中,如果我的LOCATION_服务关闭,我将获得NullPointerException。但是我想要一个alertDialog,它会提示用户激活LOCATION\u服务。谁能告诉我如何处理这个异常Java 如何避免位置服务的NullPointerException?,java,android,eclipse,google-maps,nullpointerexception,Java,Android,Eclipse,Google Maps,Nullpointerexception,在我的应用程序中,如果我的LOCATION_服务关闭,我将获得NullPointerException。但是我想要一个alertDialog,它会提示用户激活LOCATION\u服务。谁能告诉我如何处理这个异常 package com.bddevs.ddbllocator; import android.location.Location; import android.location.LocationManager; import android.os.Bundle; import
package com.bddevs.ddbllocator;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MainActivity extends ActionBarActivity {
private GoogleMap googleMap;;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
if (googleMap == null) {
googleMap = ((SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map)).getMap();
if (googleMap != null) {
setUpMap();
}
}
}
}
}
}
这是LOGCAT跟踪:
03-29 23:52:34.682:E/AndroidRuntime(11716):致命异常:主
03-29 23:52:34.682:E/AndroidRuntime(11716):java.lang.RuntimeException:无法启动活动组件信息{com.bddevs.ddbllocator/com.bddevs.ddbllocator.DBBL_LOCATOR}:java.lang.NullPointerException
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2063)
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2088)
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.ActivityThread.access$600(ActivityThread.java:134)
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.ActivityThread$H.handleMessage(ActivityThread.java:1199)
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.os.Handler.dispatchMessage(Handler.java:99)上
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.os.Looper.loop(Looper.java:137)
03-29 23:52:34.682:E/AndroidRuntime(11716):位于android.app.ActivityThread.main(ActivityThread.java:4744)
03-29 23:52:34.682:E/AndroidRuntime(11716):位于java.lang.reflect.Method.Invokenactive(本机方法)
03-29 23:52:34.682:E/AndroidRuntime(11716):位于java.lang.reflect.Method.invoke(Method.java:511)
03-29 23:52:34.682:E/AndroidRuntime(11716):在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-29 23:52:34.682:E/AndroidRuntime(11716):位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-29 23:52:34.682:E/AndroidRuntime(11716):在dalvik.system.NativeStart.main(本机方法)
03-29 23:52:34.682:E/AndroidRuntime(11716):由以下原因引起:java.lang.NullPointerException
03-29 23:52:34.682:E/AndroidRuntime(11716):在com.bddevs.ddbllocator.DBBL_LOCATOR.setUpMap(DBBL_LOCATOR.java:73)
03-29 23:52:34.682:E/AndroidRuntime(11716):在com.bddevs.ddbllocator.DBBL_LOCATOR.setupMapifneed(DBBL_LOCATOR.java:38)
03-29 23:52:34.682:E/AndroidRuntime(11716):在com.bddevs.ddbllocator.DBBL_LOCATOR.onCreate(DBBL_LOCATOR.java:29)
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.Activity.performCreate(Activity.java:5008)上
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)上
03-29 23:52:34.682:E/AndroidRuntime(11716):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2027)
03-29 23:52:34.682:E/AndroidRuntime(11716):。。。还有11个
如果位置服务被禁用。getLastKnownLocation()将返回null 添加空检查
Location myLocation = locationmanager.getLastKnownLocation(provider);
If(myLocation == null ){
// show the alert dialog
}
else {
// do your stuff with latitude and longitude
}
发布堆栈跟踪!!是的,你得到的是哪一行例外我已经发布了跟踪。它正在myLocation.getLatitude()中获取NullPointerException;当位置设备被禁用时,此行显示。我该怎么办?
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
Location myLocation = locationmanager.getLastKnownLocation(provider);
If(myLocation == null ){
// show the alert dialog
}
else {
// do your stuff with latitude and longitude
}