Android 使用 RequestFuture.get() 时截击超时异常
Android volley Timeout Exception when using RequestFuture.get()
在我的片段中，我正在尝试使用 TMDB 的开放电影数据库来获取有关 "Now Playing" 电影的详细信息。
如果我使用 RequestFuture.get(time, TimeUnit) 方法来执行此 volley 请求，我总是会收到超时错误。如果我在 Safari 中手动测试相同的 Url，我会立即得到结果。
我知道的：
1.) 这不是任何 JSON 解析错误。（程序甚至没有进行到解析步骤）
2.) AVD 没有互联网问题。 （原因稍后解释）。
3.) 我的 volley 单例 class 或我的请求队列不是问题。 （原因稍后解释）。
所以我假设我在使用 volley/Request Future 时犯了一些其他错误。
片段代码如下：
public class BoxOffice extends android.support.v4.app.Fragment {
private VolleySingleton volleySingleton;
private RequestQueue requestQueue;
private ImageLoader imageLoader;
private ArrayList<MyMovie> movieList;
private MyUriBuilder mBuilder;
public BoxOffice() {
// Required empty public constructor
volleySingleton = VolleySingleton.getInstance();
requestQueue = volleySingleton.getRequestQueue();
mBuilder = new MyUriBuilder();
movieList = new ArrayList<>();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
StepA();
}
public void StepA() {
String url = mBuilder.getURL("box");
Log.d("RT", "StepA initiated - "+ url); // Url is perfect - works when copied in Safari.
RequestFuture<JSONObject> futureA = RequestFuture.newFuture();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, (String) null, futureA, futureA);
requestQueue.add(request);
try {
JSONObject response = futureA.get(30, TimeUnit.SECONDS);
Log.d("RT", "StepA - response received"); //Never reaches this step
parseJsonFeed(response);
} catch (InterruptedException e) {
Log.e("RT", "StepA - InterruptedException - " + e);
e.printStackTrace();
} catch (ExecutionException e) {
Log.e("RT", "StepA - ExecutionException - " + e);
e.printStackTrace();
} catch (TimeoutException e) {
Log.e("RT", "StepA - TimeoutException - " + e);
e.printStackTrace();
}
Log.d("RT", "StepA END");
}
public void parseJsonFeed(JSONObject response) {
Log.d("RT", "StepA - parseFeed Begin");
if (response == null || response.length() == 0) {
return;
}
MyMovie currentMovie = null;
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
if (response.has("results")) {
Log.d("RT", "StepA - results");
JSONArray resultList = response.getJSONArray("results");
for (int i = 0; i < 3; i++) {
Log.d("RT", "movie " + i);
JSONObject movieElement = resultList.getJSONObject(i);
if (movieElement.has("id") && movieElement.has("title")) {
currentMovie = new MyMovie();
currentMovie.setTmdb_id(movieElement.getString("id"));
currentMovie.setTitle(movieElement.getString("title"));
if (movieElement.has("release_date")) {
currentMovie.setReleaseDate(dateFormat.parse(movieElement.getString("release_date")));
} else {
currentMovie.setReleaseDate(dateFormat.parse("0000-00-00"));
}
movieList.add(i, currentMovie);
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
Log.d("RT", "StepA - parseFeed END");
}
}
Logcat 使用标签过滤器 "RT":
05-30 15:17:51.710 D/RT﹕ TL - Constructor Called
05-30 15:17:51.800 D/RT﹕ StepA initiated - https://api.themoviedb.org/3/movie/now_playing?api_key=##### (link works fine)
05-30 15:18:21.820 E/RT﹕ StepA - TimeoutException - java.util.concurrent.TimeoutException
05-30 15:18:21.820 D/RT﹕ StepA END
在使用 RequestFuture 方法之前，我基本上在我的 Fragment oncreate（而不是 StepA();) 中实现了我自己的 Response.Listener 和 Response.ErrorListener，并且成功了！
下面是代码片段：
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, mBuilder.getURL("box"), (String) null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
parseJsonFeed(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity(), error.toString(), Toast.LENGTH_LONG).show();
}
});
requestQueue.add(request);
所以我的问题是为什么当我实现请求的未来方法时它不起作用？
如果你问我为什么要进行同步排球实施；这是因为在这之后我必须有两个截击请求，这取决于这个请求是否完全、成功完成。而且我也在学习:)
遗憾的是没有人可以帮助回答这个问题，但我设法解决了这个问题，如下所示：
如果 RequestFuture.get() 与 UI 线程在同一线程上，则会发生超时。我已经更改了请求的机制，以便请求在单独的异步线程（不是 UI 线程）上完成，并且响应也在与请求不同的线程上接收，如下所示：
private void StepA() {
Log.d("RT", "StepA initiated");
final CountDownLatch latchA = new CountDownLatch(1);
Thread t = new Thread(new Runnable() {
@Override
public void run() {
Log.d("RT", "Thread t Begins");
ThreadA threadA = new ThreadA();
try {
JSONObject jsonObject = threadA.execute().get(10, TimeUnit.SECONDS);
parseA(jsonObject);
latchA.countDown();
Log.d("RT", "Thread t Ends");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (TimeoutException e) {
e.printStackTrace();
}
}
});
t.start();
try {
latchA.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.d("RT", "StepA END");
}
下面是请求的异步任务代码：
protected class ThreadA extends AsyncTask<Void, Void, JSONObject> {
final String url = mBuilder.getURL("box");
public ThreadA() {
}
@Override
protected JSONObject doInBackground(Void... params) {
final RequestFuture<JSONObject> future = RequestFuture.newFuture();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, (String) null, future, future);
requestQueue.add(request);
try {
return future.get(10, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (TimeoutException e) {
e.printStackTrace();
}
return null;
}
}
我添加了倒计时锁存器，因为它们很棒，而且我的程序中很少有像这样的请求依赖于此代码段的响应。因此，它们可以更同步地帮助 运行 程序。
rapidclock 的回答很好。我个人更喜欢使用 IntentService，因为它们非常棒。另外 Google 推荐它：
https://www.youtube.com/watch?v=xHXn3Kg2IQE&t=1852s
这是我的 IntentService：
//
//http://afzaln.com/volley/com/android/volley/toolbox/RequestFuture.html
//
//
package org.peacekeeper.service;
import android.app.IntentService;
import android.content.Intent;
import android.os.*;
import com.android.volley.RequestQueue;
import org.json.JSONObject;
import org.peacekeeper.app.R;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.*;
import org.slf4j.*;
import java.util.concurrent.*;
/**
Asynchronously handles an intent using a worker thread. Receives a ResultReceiver object and a
location through an intent. Tries to fetch the address for the location using a Geocoder, and
sends the result to the ResultReceiver.
*/
public class RESTIntentService extends IntentService{
//begin static
//Intent putextra ID's
static public final String
RECEIVER = "RESTIntentServiceRCVR",
JSONResult = "JSONResult",
REQUEST = "RESTIntentServiceRequest";
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
private final static long TIMEOUT = 5;
//end static
private static final Logger mLog = LoggerFactory.getLogger( RESTIntentService.class );
//The receiver where results are forwarded from this service.
private ResultReceiver mReceiver;
//This constructor is required, and calls the super IntentService(String) constructor with the name for a worker thread.
public RESTIntentService(){ super( "RESTIntentService" ); }
@Override protected void onHandleIntent( Intent intent ){
String errorMessage = "";
mReceiver = intent.getParcelableExtra( RECEIVER );
if ( mReceiver == null ){// Check if receiver was properly registered.
mLog.error( "No RESTIntentService receiver received. There is nowhere to send the results." );
return;
}
// Get the pkRequest passed to this service through an extra.
pkRequest.pkURL URL = pkURL.valueOf( intent.getStringExtra( REQUEST ) );
mLog.debug( "RESTIntentService URL: " + URL.toString() );
// Make sure that the location data was really sent over through an extra. If it wasn't,
// send an error message and return.
if ( URL == null ){
errorMessage = getString( R.string.no_pkRequest_provided );
mLog.error( errorMessage );
deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage );
return;
}
//Request retval = null;
JSONObject response = null;
pkRequest request = new pkRequest( URL );
mLog.debug( "onHandleIntent:\n" + request.toString() );
request.submit();
try{
//while (!request.mFuture.isDone()) {;}
// TODO THIS BLOCKS the service but not the main UI thread. Consider wrapping in an asynch task:
// see
response = request.mFuture.get( TIMEOUT, TimeUnit.SECONDS );
mLog.debug( "onHandleIntent:\n" + response.toString() );
}catch ( InterruptedException | ExecutionException | TimeoutException x ){
errorMessage = getString( R.string.failed_future_request );
mLog.error( errorMessage, x );
x.printStackTrace();
}
if ( errorMessage.isEmpty() ){
deliverResultToReceiver( Constants.SUCCESS_RESULT,
response.toString() );
}
else{ deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage ); }
}//onHandleIntent()
// Sends a resultCode and message to the receiver.
private void deliverResultToReceiver( int resultCode, String message ){
Bundle bundle = new Bundle();
bundle.putString( JSONResult, message );
mReceiver.send( resultCode, bundle );
}
}//class RESTIntentService
使用 IntentService 的缺点是 IT（但不是主 UI 线程）将被 future.get(...) 阻塞。 （请参阅代码回复中的评论：future.get 块）因此，如果您正在对它进行 REST 调用，那么您可能会考虑继续使用它并按照 rapidclock 的建议将您的调用包装在异步中。
要使用上面的 IntentService，请将其放在主要 UI（或任何地方）中：
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
哦好吧...这是我的activity（请不要因为我过于详细而对我说...我爱爱爱爱 Whosebug 但好事必有报应....）：
//
package org.peacekeeper.app;
import android.Manifest;
import android.content.*;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.*;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.*;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.*;
import com.google.android.gms.maps.*;
import com.google.android.gms.maps.GoogleMap.*;
import com.google.android.gms.maps.model.*;
import com.google.android.gms.maps.model.Marker;
import org.json.JSONObject;
import org.peacekeeper.rest.LinkedRequest;
import org.peacekeeper.service.*;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.pkUtility;
import org.slf4j.*;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.util.ContextInitializer;
import ch.qos.logback.core.joran.spi.JoranException;
public class actGeocoder extends AppCompatActivity
implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener,
OnMapLongClickListener,
OnMarkerClickListener{
//begin static
private static final LoggerContext mLoggerContext =
(LoggerContext) LoggerFactory.getILoggerFactory();
private static final ContextInitializer mContextInitializer =
new ContextInitializer( mLoggerContext );
private static final Logger mLog = LoggerFactory.getLogger( actGeocoder.class );
private static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
//end static
private GoogleMap mGoogleMap;
private SupportMapFragment mapFrag;
private LocationRequest mLocationRequest;
private GoogleApiClient mGoogleApiClient;
private MarkerOptions mMarkerOptions;
private Marker mMarker;
private AddressResultReceiver mResultReceiver = new AddressResultReceiver( new Handler() );
private RESTResultReceiver mRESTResultReceiver = new RESTResultReceiver( new Handler() );
private pkUtility mUtility;
public void newPeaceKeeperStatus(){
startRESTService( pkRequest.pkURL.status );
}
@Override protected void onCreate( Bundle savedInstanceState ){
super.onCreate( savedInstanceState );
mUtility = pkUtility.getInstance( this );
newPeaceKeeperStatus();
setContentView( R.layout.geocoder );
getSupportActionBar().setTitle( R.string.RegisterYourLocn );
buildGoogleApiClient();
mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById( R.id.geocoder );
mapFrag.getMapAsync( this );
}//onCreate
@Override public void onResume(){
super.onResume();
mGoogleApiClient.connect();
}
@Override protected void onRestart(){
super.onRestart();
// Reload Logback log:
mLoggerContext.reset();
//I prefer autoConfig() over JoranConfigurator.doConfigure() so I don't need to find the file myself.
try{ mContextInitializer.autoConfig(); }
catch ( JoranException X ){ X.printStackTrace(); }
}//onRestart()
@Override protected void onStop(){
mGoogleApiClient.disconnect();
mLoggerContext.stop();//flush log
super.onStop();
}
@Override public void onDestroy(){
mLog.trace( "onDestroy():\t" );
mLoggerContext.stop();//flush log
super.onDestroy();
}
@Override public void onRequestPermissionsResult( int requestCode, String permissions[], int[] grantResults ){
switch ( requestCode ){
case MY_PERMISSIONS_REQUEST_LOCATION:{
// If request is cancelled, the result arrays are empty.
if ( grantResults.length > 0
&& grantResults[ 0 ] == PackageManager.PERMISSION_GRANTED ){
// permission was granted, yay! Do the location-related task you need to do.
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
if ( mGoogleApiClient == null ){ buildGoogleApiClient(); }
mGoogleMap.setMyLocationEnabled( true );
}
}
// permission denied. Disable the functionality that depends on this permission.
else{ Toast.makeText( this, "permission denied", Toast.LENGTH_LONG ).show(); }
return;
}
}//switch
}
protected synchronized void buildGoogleApiClient(){
mGoogleApiClient = new GoogleApiClient.Builder( this )
.addConnectionCallbacks( this )
.addOnConnectionFailedListener( this )
.addApi( LocationServices.API )
.build();
mGoogleApiClient.connect();
}
//
@Override public void onMapReady( GoogleMap googleMap ){
//Initialize Google Play Services
if ( Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ){
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
//Location Permission already granted
checkLocationPermission();
return; //Request Location Permission
}
}
mGoogleMap = googleMap;
mGoogleMap.setMapType( GoogleMap.MAP_TYPE_NORMAL );
mGoogleMap.setOnMapLongClickListener( this );
mGoogleMap.setOnMarkerClickListener(this);
mMarkerOptions = new MarkerOptions()
.title( "Tap this marker again to register your location" )
.icon( BitmapDescriptorFactory.defaultMarker( BitmapDescriptorFactory.HUE_MAGENTA) );
}
private void checkLocationPermission(){
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
// Should we show an explanation?
if ( ActivityCompat.shouldShowRequestPermissionRationale( this,
Manifest.permission.ACCESS_FINE_LOCATION ) ){
// Show an explanation to the user *asynchronously* -- don't block this thread waiting for the user's response!
// After the user sees the explanation, try again to request the permission.
new AlertDialog.Builder( this )
.setTitle( "Location Permission Needed" )
.setMessage(
"This app needs the Location permission, please accept to use location functionality" )
.setPositiveButton( "OK", new DialogInterface.OnClickListener(){
@Override public void onClick( DialogInterface dialogInterface, int i ){
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions( actGeocoder.this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
} )
.create()
.show(); }
else{ // No explanation needed, we can request the permission.
ActivityCompat.requestPermissions( this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
}
}
@Override public void onConnected( Bundle bundle ){
mLocationRequest = new LocationRequest()
.setInterval( 1000 )
.setFastestInterval( 1000 )
.setPriority( LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY );
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
LocationServices.FusedLocationApi.
requestLocationUpdates( mGoogleApiClient, mLocationRequest, this );
}
}
private final static float ZOOM = 18;
@Override public void onLocationChanged( Location location ){//this is called only once on startup.
//stop location updates since only current location is needed
LocationServices.FusedLocationApi
.removeLocationUpdates( mGoogleApiClient, this );
LatLng latLng = new LatLng( location.getLatitude(), location.getLongitude() );
mGoogleMap.moveCamera( CameraUpdateFactory.newLatLngZoom( latLng, ZOOM ) );
onMapLongClick(latLng);
}
@Override public void onMapLongClick( final LatLng latLng ){
startIntentService( latLng );
if ( mMarker != null ) mMarker.remove();
mMarkerOptions.position( latLng );
mMarker = mGoogleMap.addMarker( mMarkerOptions );
}//onMapLongClick
@Override public boolean onMarkerClick( Marker marker) {
startActivity(
new Intent(this, actRegistration.class)
.putExtra( FetchAddressIntentService.LOCATION, marker.getSnippet() )
.putExtra( FetchAddressIntentService.LATLNG, marker.getPosition() )
);
return true;
}//onMarkerClick
protected void startIntentService( final LatLng latLng ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, FetchAddressIntentService.class )
.putExtra( FetchAddressIntentService.RECEIVER, mResultReceiver )
.putExtra( FetchAddressIntentService.LATLNG, latLng )
);
}//startIntentService()
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from FetchAddressIntentService.
class AddressResultReceiver extends ResultReceiver{
public AddressResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from FetchAddressIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
mMarker.setSnippet( resultData.getString( FetchAddressIntentService.LOCATION ) );
mMarker.showInfoWindow();
}//onReceiveResult
}//class AddressResultReceiver
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
@Override public void onConnectionSuspended( int i ){ mLog.info("onConnectionSuspended: " + i );}
@Override public void onConnectionFailed( ConnectionResult connectionResult ){
mLog.error( R.string.GoogleApiClientConnFailed + ":\t" + connectionResult.getErrorMessage() );
Toast.makeText(this, R.string.GoogleApiClientConnFailed, Toast.LENGTH_LONG).show();
}
}//class actGeocoder
在我的片段中，我正在尝试使用 TMDB 的开放电影数据库来获取有关 "Now Playing" 电影的详细信息。
如果我使用 RequestFuture.get(time, TimeUnit) 方法来执行此 volley 请求，我总是会收到超时错误。如果我在 Safari 中手动测试相同的 Url，我会立即得到结果。
我知道的：
1.) 这不是任何 JSON 解析错误。（程序甚至没有进行到解析步骤）
2.) AVD 没有互联网问题。 （原因稍后解释）。
3.) 我的 volley 单例 class 或我的请求队列不是问题。 （原因稍后解释）。
所以我假设我在使用 volley/Request Future 时犯了一些其他错误。
片段代码如下：
public class BoxOffice extends android.support.v4.app.Fragment {
private VolleySingleton volleySingleton;
private RequestQueue requestQueue;
private ImageLoader imageLoader;
private ArrayList<MyMovie> movieList;
private MyUriBuilder mBuilder;
public BoxOffice() {
// Required empty public constructor
volleySingleton = VolleySingleton.getInstance();
requestQueue = volleySingleton.getRequestQueue();
mBuilder = new MyUriBuilder();
movieList = new ArrayList<>();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
StepA();
}
public void StepA() {
String url = mBuilder.getURL("box");
Log.d("RT", "StepA initiated - "+ url); // Url is perfect - works when copied in Safari.
RequestFuture<JSONObject> futureA = RequestFuture.newFuture();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, (String) null, futureA, futureA);
requestQueue.add(request);
try {
JSONObject response = futureA.get(30, TimeUnit.SECONDS);
Log.d("RT", "StepA - response received"); //Never reaches this step
parseJsonFeed(response);
} catch (InterruptedException e) {
Log.e("RT", "StepA - InterruptedException - " + e);
e.printStackTrace();
} catch (ExecutionException e) {
Log.e("RT", "StepA - ExecutionException - " + e);
e.printStackTrace();
} catch (TimeoutException e) {
Log.e("RT", "StepA - TimeoutException - " + e);
e.printStackTrace();
}
Log.d("RT", "StepA END");
}
public void parseJsonFeed(JSONObject response) {
Log.d("RT", "StepA - parseFeed Begin");
if (response == null || response.length() == 0) {
return;
}
MyMovie currentMovie = null;
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
if (response.has("results")) {
Log.d("RT", "StepA - results");
JSONArray resultList = response.getJSONArray("results");
for (int i = 0; i < 3; i++) {
Log.d("RT", "movie " + i);
JSONObject movieElement = resultList.getJSONObject(i);
if (movieElement.has("id") && movieElement.has("title")) {
currentMovie = new MyMovie();
currentMovie.setTmdb_id(movieElement.getString("id"));
currentMovie.setTitle(movieElement.getString("title"));
if (movieElement.has("release_date")) {
currentMovie.setReleaseDate(dateFormat.parse(movieElement.getString("release_date")));
} else {
currentMovie.setReleaseDate(dateFormat.parse("0000-00-00"));
}
movieList.add(i, currentMovie);
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
Log.d("RT", "StepA - parseFeed END");
}
}
Logcat 使用标签过滤器 "RT":
05-30 15:17:51.710 D/RT﹕ TL - Constructor Called
05-30 15:17:51.800 D/RT﹕ StepA initiated - https://api.themoviedb.org/3/movie/now_playing?api_key=##### (link works fine)
05-30 15:18:21.820 E/RT﹕ StepA - TimeoutException - java.util.concurrent.TimeoutException
05-30 15:18:21.820 D/RT﹕ StepA END
在使用 RequestFuture 方法之前，我基本上在我的 Fragment oncreate（而不是 StepA();) 中实现了我自己的 Response.Listener 和 Response.ErrorListener，并且成功了！
下面是代码片段：
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, mBuilder.getURL("box"), (String) null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
parseJsonFeed(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity(), error.toString(), Toast.LENGTH_LONG).show();
}
});
requestQueue.add(request);
所以我的问题是为什么当我实现请求的未来方法时它不起作用？
如果你问我为什么要进行同步排球实施；这是因为在这之后我必须有两个截击请求，这取决于这个请求是否完全、成功完成。而且我也在学习:)
遗憾的是没有人可以帮助回答这个问题，但我设法解决了这个问题，如下所示：
如果 RequestFuture.get() 与 UI 线程在同一线程上，则会发生超时。我已经更改了请求的机制，以便请求在单独的异步线程（不是 UI 线程）上完成，并且响应也在与请求不同的线程上接收，如下所示：
private void StepA() {
Log.d("RT", "StepA initiated");
final CountDownLatch latchA = new CountDownLatch(1);
Thread t = new Thread(new Runnable() {
@Override
public void run() {
Log.d("RT", "Thread t Begins");
ThreadA threadA = new ThreadA();
try {
JSONObject jsonObject = threadA.execute().get(10, TimeUnit.SECONDS);
parseA(jsonObject);
latchA.countDown();
Log.d("RT", "Thread t Ends");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (TimeoutException e) {
e.printStackTrace();
}
}
});
t.start();
try {
latchA.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.d("RT", "StepA END");
}
下面是请求的异步任务代码：
protected class ThreadA extends AsyncTask<Void, Void, JSONObject> {
final String url = mBuilder.getURL("box");
public ThreadA() {
}
@Override
protected JSONObject doInBackground(Void... params) {
final RequestFuture<JSONObject> future = RequestFuture.newFuture();
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, (String) null, future, future);
requestQueue.add(request);
try {
return future.get(10, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (TimeoutException e) {
e.printStackTrace();
}
return null;
}
}
我添加了倒计时锁存器，因为它们很棒，而且我的程序中很少有像这样的请求依赖于此代码段的响应。因此，它们可以更同步地帮助 运行 程序。
rapidclock 的回答很好。我个人更喜欢使用 IntentService，因为它们非常棒。另外 Google 推荐它： https://www.youtube.com/watch?v=xHXn3Kg2IQE&t=1852s
这是我的 IntentService：
//
//http://afzaln.com/volley/com/android/volley/toolbox/RequestFuture.html
//
//
package org.peacekeeper.service;
import android.app.IntentService;
import android.content.Intent;
import android.os.*;
import com.android.volley.RequestQueue;
import org.json.JSONObject;
import org.peacekeeper.app.R;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.*;
import org.slf4j.*;
import java.util.concurrent.*;
/**
Asynchronously handles an intent using a worker thread. Receives a ResultReceiver object and a
location through an intent. Tries to fetch the address for the location using a Geocoder, and
sends the result to the ResultReceiver.
*/
public class RESTIntentService extends IntentService{
//begin static
//Intent putextra ID's
static public final String
RECEIVER = "RESTIntentServiceRCVR",
JSONResult = "JSONResult",
REQUEST = "RESTIntentServiceRequest";
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
private final static long TIMEOUT = 5;
//end static
private static final Logger mLog = LoggerFactory.getLogger( RESTIntentService.class );
//The receiver where results are forwarded from this service.
private ResultReceiver mReceiver;
//This constructor is required, and calls the super IntentService(String) constructor with the name for a worker thread.
public RESTIntentService(){ super( "RESTIntentService" ); }
@Override protected void onHandleIntent( Intent intent ){
String errorMessage = "";
mReceiver = intent.getParcelableExtra( RECEIVER );
if ( mReceiver == null ){// Check if receiver was properly registered.
mLog.error( "No RESTIntentService receiver received. There is nowhere to send the results." );
return;
}
// Get the pkRequest passed to this service through an extra.
pkRequest.pkURL URL = pkURL.valueOf( intent.getStringExtra( REQUEST ) );
mLog.debug( "RESTIntentService URL: " + URL.toString() );
// Make sure that the location data was really sent over through an extra. If it wasn't,
// send an error message and return.
if ( URL == null ){
errorMessage = getString( R.string.no_pkRequest_provided );
mLog.error( errorMessage );
deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage );
return;
}
//Request retval = null;
JSONObject response = null;
pkRequest request = new pkRequest( URL );
mLog.debug( "onHandleIntent:\n" + request.toString() );
request.submit();
try{
//while (!request.mFuture.isDone()) {;}
// TODO THIS BLOCKS the service but not the main UI thread. Consider wrapping in an asynch task:
// see
response = request.mFuture.get( TIMEOUT, TimeUnit.SECONDS );
mLog.debug( "onHandleIntent:\n" + response.toString() );
}catch ( InterruptedException | ExecutionException | TimeoutException x ){
errorMessage = getString( R.string.failed_future_request );
mLog.error( errorMessage, x );
x.printStackTrace();
}
if ( errorMessage.isEmpty() ){
deliverResultToReceiver( Constants.SUCCESS_RESULT,
response.toString() );
}
else{ deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage ); }
}//onHandleIntent()
// Sends a resultCode and message to the receiver.
private void deliverResultToReceiver( int resultCode, String message ){
Bundle bundle = new Bundle();
bundle.putString( JSONResult, message );
mReceiver.send( resultCode, bundle );
}
}//class RESTIntentService
使用 IntentService 的缺点是 IT（但不是主 UI 线程）将被 future.get(...) 阻塞。 （请参阅代码回复中的评论：future.get 块）因此，如果您正在对它进行 REST 调用，那么您可能会考虑继续使用它并按照 rapidclock 的建议将您的调用包装在异步中。
要使用上面的 IntentService，请将其放在主要 UI（或任何地方）中：
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
哦好吧...这是我的activity（请不要因为我过于详细而对我说...我爱爱爱爱 Whosebug 但好事必有报应....）：
//
package org.peacekeeper.app;
import android.Manifest;
import android.content.*;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.*;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.*;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.*;
import com.google.android.gms.maps.*;
import com.google.android.gms.maps.GoogleMap.*;
import com.google.android.gms.maps.model.*;
import com.google.android.gms.maps.model.Marker;
import org.json.JSONObject;
import org.peacekeeper.rest.LinkedRequest;
import org.peacekeeper.service.*;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.pkUtility;
import org.slf4j.*;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.util.ContextInitializer;
import ch.qos.logback.core.joran.spi.JoranException;
public class actGeocoder extends AppCompatActivity
implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener,
OnMapLongClickListener,
OnMarkerClickListener{
//begin static
private static final LoggerContext mLoggerContext =
(LoggerContext) LoggerFactory.getILoggerFactory();
private static final ContextInitializer mContextInitializer =
new ContextInitializer( mLoggerContext );
private static final Logger mLog = LoggerFactory.getLogger( actGeocoder.class );
private static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
//end static
private GoogleMap mGoogleMap;
private SupportMapFragment mapFrag;
private LocationRequest mLocationRequest;
private GoogleApiClient mGoogleApiClient;
private MarkerOptions mMarkerOptions;
private Marker mMarker;
private AddressResultReceiver mResultReceiver = new AddressResultReceiver( new Handler() );
private RESTResultReceiver mRESTResultReceiver = new RESTResultReceiver( new Handler() );
private pkUtility mUtility;
public void newPeaceKeeperStatus(){
startRESTService( pkRequest.pkURL.status );
}
@Override protected void onCreate( Bundle savedInstanceState ){
super.onCreate( savedInstanceState );
mUtility = pkUtility.getInstance( this );
newPeaceKeeperStatus();
setContentView( R.layout.geocoder );
getSupportActionBar().setTitle( R.string.RegisterYourLocn );
buildGoogleApiClient();
mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById( R.id.geocoder );
mapFrag.getMapAsync( this );
}//onCreate
@Override public void onResume(){
super.onResume();
mGoogleApiClient.connect();
}
@Override protected void onRestart(){
super.onRestart();
// Reload Logback log:
mLoggerContext.reset();
//I prefer autoConfig() over JoranConfigurator.doConfigure() so I don't need to find the file myself.
try{ mContextInitializer.autoConfig(); }
catch ( JoranException X ){ X.printStackTrace(); }
}//onRestart()
@Override protected void onStop(){
mGoogleApiClient.disconnect();
mLoggerContext.stop();//flush log
super.onStop();
}
@Override public void onDestroy(){
mLog.trace( "onDestroy():\t" );
mLoggerContext.stop();//flush log
super.onDestroy();
}
@Override public void onRequestPermissionsResult( int requestCode, String permissions[], int[] grantResults ){
switch ( requestCode ){
case MY_PERMISSIONS_REQUEST_LOCATION:{
// If request is cancelled, the result arrays are empty.
if ( grantResults.length > 0
&& grantResults[ 0 ] == PackageManager.PERMISSION_GRANTED ){
// permission was granted, yay! Do the location-related task you need to do.
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
if ( mGoogleApiClient == null ){ buildGoogleApiClient(); }
mGoogleMap.setMyLocationEnabled( true );
}
}
// permission denied. Disable the functionality that depends on this permission.
else{ Toast.makeText( this, "permission denied", Toast.LENGTH_LONG ).show(); }
return;
}
}//switch
}
protected synchronized void buildGoogleApiClient(){
mGoogleApiClient = new GoogleApiClient.Builder( this )
.addConnectionCallbacks( this )
.addOnConnectionFailedListener( this )
.addApi( LocationServices.API )
.build();
mGoogleApiClient.connect();
}
//
@Override public void onMapReady( GoogleMap googleMap ){
//Initialize Google Play Services
if ( Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ){
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
//Location Permission already granted
checkLocationPermission();
return; //Request Location Permission
}
}
mGoogleMap = googleMap;
mGoogleMap.setMapType( GoogleMap.MAP_TYPE_NORMAL );
mGoogleMap.setOnMapLongClickListener( this );
mGoogleMap.setOnMarkerClickListener(this);
mMarkerOptions = new MarkerOptions()
.title( "Tap this marker again to register your location" )
.icon( BitmapDescriptorFactory.defaultMarker( BitmapDescriptorFactory.HUE_MAGENTA) );
}
private void checkLocationPermission(){
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
// Should we show an explanation?
if ( ActivityCompat.shouldShowRequestPermissionRationale( this,
Manifest.permission.ACCESS_FINE_LOCATION ) ){
// Show an explanation to the user *asynchronously* -- don't block this thread waiting for the user's response!
// After the user sees the explanation, try again to request the permission.
new AlertDialog.Builder( this )
.setTitle( "Location Permission Needed" )
.setMessage(
"This app needs the Location permission, please accept to use location functionality" )
.setPositiveButton( "OK", new DialogInterface.OnClickListener(){
@Override public void onClick( DialogInterface dialogInterface, int i ){
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions( actGeocoder.this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
} )
.create()
.show(); }
else{ // No explanation needed, we can request the permission.
ActivityCompat.requestPermissions( this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
}
}
@Override public void onConnected( Bundle bundle ){
mLocationRequest = new LocationRequest()
.setInterval( 1000 )
.setFastestInterval( 1000 )
.setPriority( LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY );
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
LocationServices.FusedLocationApi.
requestLocationUpdates( mGoogleApiClient, mLocationRequest, this );
}
}
private final static float ZOOM = 18;
@Override public void onLocationChanged( Location location ){//this is called only once on startup.
//stop location updates since only current location is needed
LocationServices.FusedLocationApi
.removeLocationUpdates( mGoogleApiClient, this );
LatLng latLng = new LatLng( location.getLatitude(), location.getLongitude() );
mGoogleMap.moveCamera( CameraUpdateFactory.newLatLngZoom( latLng, ZOOM ) );
onMapLongClick(latLng);
}
@Override public void onMapLongClick( final LatLng latLng ){
startIntentService( latLng );
if ( mMarker != null ) mMarker.remove();
mMarkerOptions.position( latLng );
mMarker = mGoogleMap.addMarker( mMarkerOptions );
}//onMapLongClick
@Override public boolean onMarkerClick( Marker marker) {
startActivity(
new Intent(this, actRegistration.class)
.putExtra( FetchAddressIntentService.LOCATION, marker.getSnippet() )
.putExtra( FetchAddressIntentService.LATLNG, marker.getPosition() )
);
return true;
}//onMarkerClick
protected void startIntentService( final LatLng latLng ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, FetchAddressIntentService.class )
.putExtra( FetchAddressIntentService.RECEIVER, mResultReceiver )
.putExtra( FetchAddressIntentService.LATLNG, latLng )
);
}//startIntentService()
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from FetchAddressIntentService.
class AddressResultReceiver extends ResultReceiver{
public AddressResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from FetchAddressIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
mMarker.setSnippet( resultData.getString( FetchAddressIntentService.LOCATION ) );
mMarker.showInfoWindow();
}//onReceiveResult
}//class AddressResultReceiver
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
@Override public void onConnectionSuspended( int i ){ mLog.info("onConnectionSuspended: " + i );}
@Override public void onConnectionFailed( ConnectionResult connectionResult ){
mLog.error( R.string.GoogleApiClientConnFailed + ":\t" + connectionResult.getErrorMessage() );
Toast.makeText(this, R.string.GoogleApiClientConnFailed, Toast.LENGTH_LONG).show();
}
}//class actGeocoder