有人可以帮我弄清楚为什么AsyncTask会偶尔崩溃吗？
继承我的守则：
public class statuspage extends MapActivity {
LocationManager locationManager;
MapView mapView;
Criteria criteria;
Location location;
Geocoder gc;
Address address;
String bestProvider;
String LOCATION_SERVICE = "location";
String addressString = "No address found";
StringBuilder sb;
private MapController mapController;
private MyLocationOverlay myLocation;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.statuspage);
// Get Mapping Controllers etc //
mapView = (MapView) findViewById(R.id.mapView);
mapController = mapView.getController();
mapController.setZoom(17);
mapView.setBuiltInZoomControls(true);
// Add the MyLocationOverlay //
myLocation = new MyLocationOverlay(this, mapView);
mapView.getOverlays().add(myLocation);
myLocation.enableMyLocation();
// Animates the map to GPS Position //
myLocation.runOnFirstFix(new Runnable() {
public void run() {
mapController.animateTo(myLocation.getMyLocation());
}
});
}
@Override
protected boolean isRouteDisplayed() {
// Executes GeoCoding AsyncTask //
new GeoCoder().execute();
// Location Manager Intiation
locationManager = (LocationManager) statuspage.this
.getSystemService(LOCATION_SERVICE);
criteria = new Criteria();
// More accurate, GPS fix.
criteria.setAccuracy(Criteria.ACCURACY_FINE); // More accurate, GPS fix.
bestProvider = locationManager.getBestProvider(criteria, true);
location = locationManager.getLastKnownLocation(bestProvider);
if (location != null) {
// Latitude and Longitude TextView
TextView etlongitude = (TextView) findViewById(R.id.etlongitude);
TextView etlatitude = (TextView) findViewById(R.id.etlatitude);
double latitude = location.getLatitude();
double longitude = location.getLongitude();
// Latitude and Longitude TextView Display Coordinates //
etlongitude.setText((longitude) + "");
etlatitude.setText((latitude) + "");
// locationManager.removeUpdates((LocationListener) location);
locationManager = null;
}
return false;
}
class GeoCoder extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
Log.d("Class == GeoCoder", "AsyncTask == doInBackGround");
double latitude = location.getLatitude();
double longitude = location.getLongitude();
gc = new Geocoder(statuspage.this, Locale.getDefault());
try {
List<Address> addresses = gc.getFromLocation(latitude,
longitude, 1);
sb = new StringBuilder();
if (addresses != null && addresses.size() > 0) {
address = addresses.get(0);
int noOfMaxAddressLine = address.getMaxAddressLineIndex();
if (noOfMaxAddressLine > 0) {
for (int i = 0; i < address.getMaxAddressLineIndex(); i++) {
sb.append(address.getAddressLine(i)).append("\n");
}
addressString = sb.toString();
}
}
} catch (Exception e) {
addressString = e.toString();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
TextView scrollview = (TextView) findViewById(R.id.scrollview);
scrollview.setText("Your location:" + "\n"
+ "(Accurate to 500 meters)" + "\n" + (addressString));
Log.d("Class == GeoCoder", "AsyncTask == onPostExecute");
return;
}
}
@Override
protected void onResume() {
super.onResume();
myLocation.enableMyLocation();
}
@Override
protected void onDestroy() {
super.onDestroy();
new GeoCoder();
}
@Override
protected void onPause() {
super.onPause();
new GeoCoder().cancel(true);
myLocation.disableMyLocation();
}
@Override
public void onStop() {
super.onStop();
new GeoCoder().cancel(true);
}
@Override
public void onBackPressed() {
new GeoCoder().cancel(true);
// Button OnClick Vibrating Service
Vibrator vib = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
// Vibrate Service
vib.vibrate(50);
startActivity(new Intent(statuspage.this, AgentPortalActivity.class));
statuspage.this.finish();
/** Fading Transition Effect */
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
return;
}
}
继承我的日志：
04-20 09:23:15.449: D/Class == GeoCoder(22493): AsyncTask == onPostExecute
04-20 09:23:16.082: D/Dialog(22493): dialog button was clicked
04-20 09:23:16.136: W/MapActivity(22493): Recycling dispatcher android_maps_conflict_avoidance.com.google.googlenav.datarequest.DataRequestDispatcher@40685938
04-20 09:23:16.140: V/MapActivity(22493): Recycling map object.
04-20 09:23:16.167: I/Maps.MyLocationOverlay(22493): Request updates from gps
04-20 09:23:16.167: I/Maps.MyLocationOverlay(22493): Request updates from network
04-20 09:23:16.179: I/Maps.MyLocationOverlay(22493): Request updates from gps
04-20 09:23:16.183: I/Maps.MyLocationOverlay(22493): Request updates from network
04-20 09:23:16.238: I/MapActivity(22493): Handling network change notification:CONNECTED
04-20 09:23:16.238: E/MapActivity(22493): Couldn't get connection factory client
04-20 09:23:16.281: D/Class == GeoCoder(22493): AsyncTask == doInBackGround
04-20 09:23:16.300: W/dalvikvm(22493): threadid=28: thread exiting with uncaught exception (group=0x40015578)
04-20 09:23:16.390: E/AndroidRuntime(22493): FATAL EXCEPTION: AsyncTask #16
04-20 09:23:16.390: E/AndroidRuntime(22493): java.lang.RuntimeException: An error occured while executing doInBackground()
04-20 09:23:16.390: E/AndroidRuntime(22493): at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.lang.Thread.run(Thread.java:1019)
04-20 09:23:16.390: E/AndroidRuntime(22493): Caused by: java.lang.NullPointerException
04-20 09:23:16.390: E/AndroidRuntime(22493): at com.jetdelivery.mobile.statuspage$GeoCoder.doInBackground(statuspage.java:111)
04-20 09:23:16.390: E/AndroidRuntime(22493): at com.jetdelivery.mobile.statuspage$GeoCoder.doInBackground(statuspage.java:1)
04-20 09:23:16.390: E/AndroidRuntime(22493): at android.os.AsyncTask$2.call(AsyncTask.java:185)
04-20 09:23:16.390: E/AndroidRuntime(22493): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
04-20 09:23:16.390: E/AndroidRuntime(22493): ... 4 more
Heres 111行： double latitude = location.getLatitude（）;
我一直试图弄清楚这几天，尝试在这里搜索，在谷歌上，跟着一些例子，没有运气。
谢谢你们！
答案 0 :(得分：2)
在isRouteDisplayed（）中初始化位置对象之前启动GeoCoder任务。您应该在获取位置并测试null后启动它，这意味着在行之后：
if (location != null) {
您还可以在doInBackground中测试它是否为空指针，但没有它，整个方法看起来没用。
有时会发生崩溃，因为您不知道任务何时开始。这意味着有时创建GeoCoder任务的线程将继续运行，初始化位置对象而不是任务控制。但是，这有时会发生。在其他情况下，任务在第一个线程到达位置和崩溃的初始化代码之前开始。