Clarify threading when loading categories
Previously, it was not explicit that the `onCreate` happened to be invoked in the UI thread. Now it is, due to passing `new Handler(Looper.getMainLooper())`. Also, the categories are now loaded in a background task, and then the UI is updated on the UI thread.
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@ -7,7 +7,10 @@ import android.content.res.Resources;
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import android.database.ContentObserver;
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import android.database.Cursor;
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import android.net.Uri;
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import android.os.AsyncTask;
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import android.os.Bundle;
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import android.os.Handler;
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import android.os.Looper;
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import android.support.annotation.Nullable;
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import android.support.v4.app.LoaderManager;
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import android.view.LayoutInflater;
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@ -72,27 +75,34 @@ public class AvailableAppsFragment extends AppListFragment implements
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private final ArrayAdapter<String> adapter;
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CategoryObserver(ArrayAdapter<String> adapter) {
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super(null);
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// Using Looper.getMainLooper() ensures that the onChange method is run on the main thread.
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super(new Handler(Looper.getMainLooper()));
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this.adapter = adapter;
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}
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@Override
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public void onChange(boolean selfChange) {
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// Wanted to just do this update here, but android tells
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// me that "Only the original thread that created a view
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// hierarchy can touch its views."
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final Activity activity = getActivity();
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if (!isAdded() || adapter == null || activity == null) {
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return;
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}
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activity.runOnUiThread(new Runnable() {
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// Because onChange is always invoked on the main thread (see constructor), we want to
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// run the database query on a background thread. Afterwards, the UI is updated
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// on a foreground thread.
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new AsyncTask<Void, Void, List<String>>() {
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@Override
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public void run() {
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adapter.clear();
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categories = AppProvider.Helper.categories(activity);
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ArrayAdapterCompat.addAll(adapter, translateCategories(categories));
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protected List<String> doInBackground(Void... params) {
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return AppProvider.Helper.categories(activity);
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}
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});
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@Override
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protected void onPostExecute(List<String> loadedCategories) {
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adapter.clear();
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categories = loadedCategories;
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ArrayAdapterCompat.addAll(adapter, translateCategories(loadedCategories));
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}
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}.execute();
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}
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@Override
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