Hi. I need to migrate an Android application developed with the ESRI SDK 10.2.8 to the newest SDK: 100.6. My first big obstacle is migrating all the queries. Currently, they are done with the object QueryTask (which doesn't exist any longer). With it, I get the response from the server, I send the data with a return to the next step. Now, it seems that all queries are asynchronous, so the data that is returned is always empty. How can I get a synchronous behaviour with the new SDK? I'm totally stuck. ArrayList Community > communities = new ArrayList Community > ( ) ; QueryParameters query = new QueryParameters ( ) ; // WHERE StringBuilder whereStrBuilder = new StringBuilder ( ) ; whereStrBuilder . append ( "display_order > 0" ) ; query . setWhereClause ( whereStrBuilder . toString ( ) ) ; // ORDER OrderBy order = new OrderBy ( "display_order" , SortOrder . ASCENDING ) ; query . getOrderByFields ( ) . add ( order ) ; query . setReturnGeometry ( false ) ; final ListenableFuture FeatureQueryResult > future = Layer . SERVICE_COMMUNITY . queryFeaturesAsync ( query , ServiceFeatureTable . QueryFeatureFields . LOAD_ALL ) ; future . addDoneListener ( new Runnable ( ) { @Override public void run ( ) { try { // check if server result successful FeatureQueryResult result = future . get ( ) ; // check there are some results Iterator Feature > resultIterator = result . iterator ( ) ; while ( resultIterator . hasNext ( ) ) { Feature feature = resultIterator . next ( ) ; communities . add ( featureToCommunity ( feature ) ) ; } } catch ( Exception e ) { } } } ) ; return communities ; communities is always empry, because it is returned before the addDoneListener is triggered. Is there a way of making the process wait until the query has finished so the proper list of communities is returned? Thanks for any help provided!

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SDK 100.6 - How to perform a synchronous Query?

OscarDiago_Alonso

Hi.

I need to migrate an Android application developed with the ESRI SDK 10.2.8 to the newest SDK: 100.6.

My first big obstacle is migrating all the queries. Currently, they are done with the object QueryTask (which doesn't exist any longer). With it, I get the response from the server, I send the data with a return to the next step.

Now, it seems that all queries are asynchronous, so the data that is returned is always empty. How can I get a synchronous behaviour with the new SDK? I'm totally stuck.

ArrayList<SPAN class="operator token"><</SPAN>Community<SPAN class="operator token">></SPAN> communities <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">ArrayList</SPAN><SPAN class="operator token"><</SPAN>Community<SPAN class="operator token">></SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

QueryParameters query <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">QueryParameters</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
				
<SPAN class="comment token">// WHERE</SPAN>
StringBuilder whereStrBuilder <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">StringBuilder</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
whereStrBuilder<SPAN class="punctuation token">.</SPAN><SPAN class="token function">append</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"display_order > 0"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
query<SPAN class="punctuation token">.</SPAN><SPAN class="token function">setWhereClause</SPAN><SPAN class="punctuation token">(</SPAN>whereStrBuilder<SPAN class="punctuation token">.</SPAN><SPAN class="token function">toString</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
			
<SPAN class="comment token">// ORDER		</SPAN>
OrderBy order <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">OrderBy</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"display_order"</SPAN><SPAN class="punctuation token">,</SPAN> SortOrder<SPAN class="punctuation token">.</SPAN>ASCENDING<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
query<SPAN class="punctuation token">.</SPAN><SPAN class="token function">getOrderByFields</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">add</SPAN><SPAN class="punctuation token">(</SPAN>order<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
					
query<SPAN class="punctuation token">.</SPAN><SPAN class="token function">setReturnGeometry</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="token boolean">false</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

			
<SPAN class="keyword token">final</SPAN> ListenableFuture<SPAN class="operator token"><</SPAN>FeatureQueryResult<SPAN class="operator token">></SPAN> future <SPAN class="operator token">=</SPAN> Layer<SPAN class="punctuation token">.</SPAN>SERVICE_COMMUNITY<SPAN class="punctuation token">.</SPAN><SPAN class="token function">queryFeaturesAsync</SPAN><SPAN class="punctuation token">(</SPAN>query<SPAN class="punctuation token">,</SPAN> ServiceFeatureTable<SPAN class="punctuation token">.</SPAN>QueryFeatureFields<SPAN class="punctuation token">.</SPAN>LOAD_ALL<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

future<SPAN class="punctuation token">.</SPAN><SPAN class="token function">addDoneListener</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">Runnable</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
	                @Override
	                <SPAN class="keyword token">public</SPAN> <SPAN class="keyword token">void</SPAN> <SPAN class="token function">run</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
	                  <SPAN class="keyword token">try</SPAN> <SPAN class="punctuation token">{</SPAN>

	                    <SPAN class="comment token">// check if server result successful</SPAN>
	                	FeatureQueryResult result <SPAN class="operator token">=</SPAN> future<SPAN class="punctuation token">.</SPAN><SPAN class="token function">get</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
	                	<SPAN class="comment token">// check there are some results</SPAN>
	      		        Iterator<SPAN class="operator token"><</SPAN>Feature<SPAN class="operator token">></SPAN> resultIterator <SPAN class="operator token">=</SPAN> result<SPAN class="punctuation token">.</SPAN><SPAN class="token function">iterator</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
	      		      <SPAN class="keyword token">while</SPAN> <SPAN class="punctuation token">(</SPAN>resultIterator<SPAN class="punctuation token">.</SPAN><SPAN class="token function">hasNext</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
	      		    	Feature feature <SPAN class="operator token">=</SPAN> resultIterator<SPAN class="punctuation token">.</SPAN><SPAN class="token function">next</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
	      		    	communities<SPAN class="punctuation token">.</SPAN><SPAN class="token function">add</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="token function">featureToCommunity</SPAN><SPAN class="punctuation token">(</SPAN>feature<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
	      		      <SPAN class="punctuation token">}</SPAN>
	                  <SPAN class="punctuation token">}</SPAN> <SPAN class="keyword token">catch</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="token class-name">Exception</SPAN> e<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>

	                  <SPAN class="punctuation token">}</SPAN>
	                <SPAN class="punctuation token">}</SPAN>
	              <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

<SPAN class="keyword token">return</SPAN> communities<SPAN class="punctuation token">;</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

communities is always empry, because it is returned before the addDoneListener is triggered. Is there a way of making the process wait until the query has finished so the proper list of communities is returned?

Thanks for any help provided!

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Accepted answers

MarkBaird

A future is a promise to return something. You can use this asynchronously as you've show above and listen into a callback to tell you the result is ready. This will call back on a separate thread.

Futures can also be made to block the thread you are on until the result comes through. If you don't bother listening to the done event, you can just call future.get.

However be careful that you are not using this on the UI thread of your app!!!

All comments

OscarDiago_Alonso

Thanks for your answer!! I made it work

The migration to the new SDK is being more of a headache than I was expecting.

MarkBaird

A future is a promise to return something. You can use this asynchronously as you've show above and listen into a callback to tell you the result is ready. This will call back on a separate thread.

Futures can also be made to block the thread you are on until the result comes through. If you don't bother listening to the done event, you can just call future.get.

However be careful that you are not using this on the UI thread of your app!!!

OscarDiago_Alonso

I will answer myself:

<SPAN class="keyword token">final</SPAN> ListenableFuture<SPAN class="operator token"><</SPAN>FeatureQueryResult<SPAN class="operator token">></SPAN> future <SPAN class="operator token">=</SPAN> Layer<SPAN class="punctuation token">.</SPAN>SERVICE_COMMUNITY<SPAN class="punctuation token">.</SPAN><SPAN class="token function">queryFeaturesAsync</SPAN><SPAN class="punctuation token">(</SPAN>query<SPAN class="punctuation token">,</SPAN> ServiceFeatureTable<SPAN class="punctuation token">.</SPAN>QueryFeatureFields<SPAN class="punctuation token">.</SPAN>LOAD_ALL<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

<SPAN class="comment token">// check if server result successful</SPAN>
FeatureQueryResult result <SPAN class="operator token">=</SPAN> future<SPAN class="punctuation token">.</SPAN><SPAN class="token function">get</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="comment token">// check there are some results</SPAN>
Iterator<SPAN class="operator token"><</SPAN>Feature<SPAN class="operator token">></SPAN> resultIterator <SPAN class="operator token">=</SPAN> result<SPAN class="punctuation token">.</SPAN><SPAN class="token function">iterator</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="keyword token">while</SPAN> <SPAN class="punctuation token">(</SPAN>resultIterator<SPAN class="punctuation token">.</SPAN><SPAN class="token function">hasNext</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
      Feature feature <SPAN class="operator token">=</SPAN> resultIterator<SPAN class="punctuation token">.</SPAN><SPAN class="token function">next</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
      communities<SPAN class="punctuation token">.</SPAN><SPAN class="token function">add</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="token function">featureToCommunity</SPAN><SPAN class="punctuation token">(</SPAN>feature<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="punctuation token">}</SPAN>

<SPAN class="keyword token">return</SPAN> communities<SPAN class="punctuation token">;</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

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