Implemented Parallel Download of Forms using Multi-Threading and Locks

odk/collect/collect_app/src/main/java/org/odk/collect/android/formmanagement/ServerFormDownloader.java

@@ -22,6 +22,8 @@
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Supplier;
 
 import javax.annotation.Nullable;
@@ -46,6 +48,8 @@ public ServerFormDownloader(FormSource formSource, FormsRepository formsReposito
         this.clock = clock;
     }
 
+    private static Lock lock = new ReentrantLock();
+
     @Override
     public void downloadForm(ServerFormDetails form, @Nullable ProgressReporter progressReporter, @Nullable Supplier<Boolean> isCancelled) throws FormDownloadException {
         Form formOnDevice;
@@ -94,8 +98,8 @@ private void processOneForm(ServerFormDetails fd, OngoingWorkListener stateListe
             // get the xml file
             // if we've downloaded a duplicate, this gives us the file
             fileResult = downloadXform(fd.getFormName(), fd.getDownloadUrl(), stateListener, tempDir, formsDirPath);
-
             // download media files if there are any
+            lock.lock();
             if (fd.getManifest() != null && !fd.getManifest().getMediaFiles().isEmpty()) {
                 FormMediaDownloader mediaDownloader = new FormMediaDownloader(formsRepository, formSource);
                 newAttachmentsDetected = mediaDownloader.download(fd, fd.getManifest().getMediaFiles(), tempMediaPath, tempDir, stateListener);
@@ -138,6 +142,7 @@ private void processOneForm(ServerFormDetails fd, OngoingWorkListener stateListe
 
         try {
             installEverything(tempMediaPath, fileResult, parsedFields, formsDirPath, newAttachmentsDetected);
+            lock.unlock();
         } catch (FormDownloadException.DiskError e) {
             cleanUp(fileResult, tempMediaPath);
             throw e;

odk/collect/collect_app/src/main/java/org/odk/collect/android/tasks/DownloadFormsTask.java

@@ -18,6 +18,8 @@
 import static java.util.Collections.emptyMap;
 
 import android.os.AsyncTask;
+import android.os.Handler;
+import android.os.Looper;
 
 import org.odk.collect.android.R;
 import org.odk.collect.android.application.Collect;
@@ -30,6 +32,8 @@
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 /**
  * Background task for downloading a given list of forms. We assume right now that the forms are
@@ -53,34 +57,48 @@ public DownloadFormsTask(FormDownloader formDownloader) {
     protected Map<ServerFormDetails, FormDownloadException> doInBackground(ArrayList<ServerFormDetails>... values) {
         HashMap<ServerFormDetails, FormDownloadException> results = new HashMap<>();
 
+        ExecutorService executorService = Executors.newCachedThreadPool();
         int index = 1;
         for (ServerFormDetails serverFormDetails : values[0]) {
-            try {
-                String currentFormNumber = String.valueOf(index);
-                String totalForms = String.valueOf(values[0].size());
-                publishProgress(serverFormDetails.getFormName(), currentFormNumber, totalForms);
-
-                formDownloader.downloadForm(serverFormDetails, count -> {
-                    String message = getLocalizedString(Collect.getInstance(), R.string.form_download_progress,
-                            serverFormDetails.getFormName(),
-                            String.valueOf(count),
-                            String.valueOf(serverFormDetails.getManifest().getMediaFiles().size())
-                    );
-
-                    publishProgress(message, currentFormNumber, totalForms);
-                }, this::isCancelled);
-
-                results.put(serverFormDetails, null);
-                FormEventBus.INSTANCE.formDownloaded(serverFormDetails.getFormId());
-            } catch (FormDownloadException.DownloadingInterrupted e) {
-                return emptyMap();
-            } catch (FormDownloadException e) {
-                results.put(serverFormDetails, e);
-                FormEventBus.INSTANCE.formDownloadFailed(serverFormDetails.getFormId(), e.getMessage());
-            }
+            String currentFormNumber = String.valueOf(index);
+            String totalForms = String.valueOf(values[0].size());
+            publishProgress(serverFormDetails.getFormName(), currentFormNumber, totalForms);
+
+            Thread thread = new Thread() {
+                public void run() {
+
+                    try {
+                        formDownloader.downloadForm(serverFormDetails, count -> {
+                            String message = getLocalizedString(Collect.getInstance(), R.string.form_download_progress,
+                                    serverFormDetails.getFormName(),
+                                    String.valueOf(count),
+                                    String.valueOf(serverFormDetails.getManifest().getMediaFiles().size())
+                            );
+
+                            publishProgress(message, currentFormNumber, totalForms);
+
+                        }, DownloadFormsTask.this::isCancelled);
+                    } catch (FormDownloadException e) {
+                        results.put(serverFormDetails, e);
+                        FormEventBus.INSTANCE.formDownloadFailed(serverFormDetails.getFormId(), e.getMessage());
+                        throw new RuntimeException(e);
+                    }
+
+                    new Handler(Looper.getMainLooper()).post(new Runnable() {
+                        @Override
+                        public void run() {
+                            results.put(serverFormDetails, null);
+                            FormEventBus.INSTANCE.formDownloaded(serverFormDetails.getFormId());
+                        }
+                    });
+                }
+            };
+
+            executorService.submit(thread);
 
             index++;
         }
+        executorService.shutdown();
 
         return results;
     }