有人知道为什么AsyncTask会一直崩溃吗？基本上在我的应用程序中，我想获得GPS坐标，并将其设置为我在mapview中的位置。然后我想使用GeoCode显示我的位置的当前地址。
在我开始尝试使用AsyncTask之前，应用程序完美显示了所有内容，（在地图上显示当前位置，并告诉我哪个地址离我最近并在文本视图中显示）然而，由于我没有实现，因此它非常缓慢且滞后的AsyncTask。现在我已经实现了AsyncTask，它给了我错误。有人可以帮忙吗？
继承我的代码：
public class statuspage extends MapActivity {
private MapController mapController;
private MyLocationOverlay myLocation;
Location location;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.statuspage);
new MapOverlay().execute();
// Get Mapping Controllers etc
MapView mapView = (MapView) findViewById(R.id.mapView);
mapController = mapView.getController();
mapController.setZoom(14);
mapView.setBuiltInZoomControls(true);
// Add the MyLocationOverlay
myLocation = new MyLocationOverlay(this, mapView);
mapView.getOverlays().add(myLocation);
myLocation.enableMyLocation();
myLocation.runOnFirstFix(new Runnable() {
public void run() {
mapController.animateTo(myLocation.getMyLocation());
}
});
}
class MapOverlay extends AsyncTask<Void,Long,DataPackage> {
@Override
protected DataPackage doInBackground(Void... arg0) {
return new DataPackage();
}
}
class DataPackage {
public String addressString = null;
double latitude = location.getLatitude();
double longitude = location.getLongitude();
public DataPackage(addressString, latitude, longitude) {
statuspage.this.addressString = addressString;
statuspage.this.latitude = location.getLatitude();
statuspage.this.longitude = location.getLongitude();
}
}
protected boolean isRouteDisplayed() {
// Location Manager Intiation
LocationManager locationManager;
String bestProvider;
String LOCATION_SERVICE = "location";
locationManager = (LocationManager) statuspage.this
.getSystemService(LOCATION_SERVICE);
Criteria 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);
// Disables longitude textview Keyboard Popup.
//InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
//imm.hideSoftInputFromWindow(etlongitude.getWindowToken(), 0);
// Disables latitude textview Keyboard Popup.
//InputMethodManager imm2 = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
//imm2.hideSoftInputFromWindow(etlatitude.getWindowToken(), 0);
// Latitude and Longitude TextView Display Coordinates
etlongitude.setText("Longitude:" + "\n" + (longitude));
/** longitude textview */
etlatitude.setText("Latitude:" + "\n" + (latitude));
/** latitude textview */
addressString = "No address found";
Geocoder gc = new Geocoder(statuspage.this, Locale.getDefault());
try {
List<Address> addresses = gc.getFromLocation(latitude,
longitude, 1);
StringBuilder sb = new StringBuilder();
if (addresses.size() > 0) {
Address address = addresses.get(0);
for (int i = 0; i < address.getMaxAddressLineIndex(); i++)
sb.append(address.getAddressLine(i)).append("\n");
//sb.append(address.getFeatureName()).append("\n");
//sb.append(address.getPhone()).append("\n");
//sb.append(address.getLocality()).append("\n");
//sb.append(address.getPostalCode()).append("\n");
//sb.append(address.getCountryName());
}
addressString = sb.toString();
TextView scrollview = (TextView) findViewById(R.id.scrollview);
scrollview.setText("Your location:" + "\n" + "(Accurate to 500 meters)" +"\n" +(addressString));
} catch (IOException e) {
}
// locationManager.removeUpdates((LocationListener) location);
locationManager = null;
} else {
}
return false;
}
protected void onResume() {
myLocation.enableMyLocation();
}
protected void onPause() {
myLocation.disableMyLocation();
}
public void onBackPressed() {
// 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;
}
}
@Override
protected boolean isRouteDisplayed() {
// TODO Auto-generated method stub
return false;
}
}
以下是我的日志：
04-12 09:14:15.682: W/dalvikvm(13103): threadid=11: thread exiting with uncaught exception (group=0x40015578)
04-12 09:14:15.686: E/AndroidRuntime(13103): FATAL EXCEPTION: AsyncTask #1
04-12 09:14:15.686: E/AndroidRuntime(13103): java.lang.RuntimeException: An error occured while executing doInBackground()
04-12 09:14:15.686: E/AndroidRuntime(13103): at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.lang.Thread.run(Thread.java:1019)
04-12 09:14:15.686: E/AndroidRuntime(13103): Caused by: java.lang.NullPointerException
04-12 09:14:15.686: E/AndroidRuntime(13103): at com.jetdelivery.mobile.statuspage$MapOverlay.doInBackground(statuspage.java:119)
04-12 09:14:15.686: E/AndroidRuntime(13103): at com.jetdelivery.mobile.statuspage$MapOverlay.doInBackground(statuspage.java:1)
04-12 09:14:15.686: E/AndroidRuntime(13103): at android.os.AsyncTask$2.call(AsyncTask.java:185)
04-12 09:14:15.686: E/AndroidRuntime(13103): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
04-12 09:14:15.686: E/AndroidRuntime(13103): ... 4 more
谢谢，伙计们。
答案 0 :(得分：2)
TextView scrollview = (TextView) findViewById(R.id.scrollview);
scrollview.setText("Your location:" + "\n"
+ "(Accurate to 500 meters)" + "\n" + (addressString));
在onPostExecute（）中编写上面的代码而不是在doInBackground（）中。 在doInbackground（）中，我们只做网络相关的任务，所有与UI相关的任务必须在onPostExecute（）中。
答案 1 :(得分：1)
您的代码正在崩溃您的应用程序，因为您试图在没有处理程序且处于错误执行区域的UI线程上访问控件。
您应该阅读AsyncTask以及如何正确处理与UI的互动。该页面上有非常好的信息。
要更新您的用户界面，您应该实施
onPostExecute()，它会传递doInBackground()的结果并在UI线程中运行，因此您可以安全地更新用户界面。
您需要将相关的破解代码移至onPostExecute()：
// Latitude and Longitude TextView Display Coordinates
etlongitude.setText("Longitude:" + "\n" + (longitude));
/** longitude textview */
etlatitude.setText("Latitude:" + "\n" + (latitude));
/** latitude textview */
TextView scrollview = (TextView) findViewById(R.id.scrollview);
scrollview.setText("Your location:" + "\n"
+ "(Accurate to 500 meters)" + "\n" + (addressString));
修改：在评论讨论中添加了示例。
class DataPackage {
public String Address = null;
public double Latitude = 0.0;
public double Longitude = 0.0;
public DataPackage(address, lat, lon) {
this.Address = address;
this.Latitude = lat;
this.Longitude = lon;
}
}
...
class MapOverlay extends AsyncTask<Void,Void,DataPackage> {
@Override
protected Void doInBackground(Void... arg0) {
// ... Conditions and logic TRUNCATED for Clarity!
// This would exist inside of your try block
return new DataPackage(addressString, latitude, longitude);
// ... Rest of code
}
//...
protected void onPostExecute(DataPackage result) {
//Logic that updates the UI based on information in DataPackage object.
}
}