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Implement ParseQueryPager #129

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Merged
merged 1 commit into from
Feb 5, 2016
Merged

Implement ParseQueryPager #129

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6 changes: 5 additions & 1 deletion ParseUI-Widget-Sample/src/main/java/com/parse/ui/widget/sample/ListActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ListView;
import android.widget.Toast;

Expand All @@ -16,6 +17,8 @@

public class ListActivity extends AppCompatActivity {

private static final String TAG = "ListActivity";

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Expand All @@ -36,11 +39,12 @@ public ParseQuery<ParseObject> create() {
adapter.addOnQueryLoadListener(new ParseQueryAdapter.OnQueryLoadListener<ParseObject>() {
@Override
public void onLoading() {

Log.d(TAG, "loading");
}

@Override
public void onLoaded(List<ParseObject> objects, Exception e) {
Log.d(TAG, "loaded");
if (e != null
&& e instanceof ParseException
&& ((ParseException) e).getCode() != ParseException.CACHE_MISS) {
Expand Down
199 changes: 69 additions & 130 deletions ParseUI-Widget/src/main/java/com/parse/ParseQueryAdapter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,17 +32,14 @@
import android.widget.LinearLayout;
import android.widget.TextView;

import com.parse.ParseQuery.CachePolicy;
import com.parse.widget.util.ParseQueryPager;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;

import bolts.Capture;
import bolts.CancellationTokenSource;

/**
* A {@code ParseQueryAdapter} handles the fetching of objects by page, and displaying objects as
Expand Down Expand Up @@ -112,15 +109,23 @@ public interface OnQueryLoadListener<T extends ParseObject> {
void onLoaded(List<T> objects, Exception e);
}

private final Object lock = new Object();
private ParseQueryPager<T> pager;
private CancellationTokenSource cts;

//region Backwards compatibility
private ParseQuery<T> query;
private int objectsPerPage = 25;
//endregion

private Integer itemResourceId;

// The key to use to display on the cell text label.
private String textKey;

// The key to use to fetch an image for display in the cell's image view.
private String imageKey;

// The number of objects to show per page (default: 25)
private int objectsPerPage = 25;

// Whether the table should use the built-in pagination feature (default:
// true)
private boolean paginationEnabled = true;
Expand All @@ -142,24 +147,6 @@ public interface OnQueryLoadListener<T extends ParseObject> {

private Context context;

private List<T> objects = new ArrayList<>();

private Set<ParseQuery> runningQueries =
Collections.newSetFromMap(new ConcurrentHashMap<ParseQuery, Boolean>());


// Used to keep track of the pages of objects when using CACHE_THEN_NETWORK. When using this,
// the data will be flattened and put into the objects list.
private List<List<T>> objectPages = new ArrayList<>();

private int currentPage = 0;

private Integer itemResourceId;

private boolean hasNextPage = true;

private QueryFactory<T> queryFactory;

private List<OnQueryLoadListener<T>> onQueryLoadListeners =
new ArrayList<>();

Expand Down Expand Up @@ -277,7 +264,7 @@ public ParseQueryAdapter(Context context, QueryFactory<T> queryFactory, int item
private ParseQueryAdapter(Context context, QueryFactory<T> queryFactory, Integer itemViewResource) {
super();
this.context = context;
this.queryFactory = queryFactory;
query = queryFactory.create();
itemResourceId = itemViewResource;
}

Expand All @@ -290,13 +277,38 @@ public Context getContext() {
return context;
}

private ParseQueryPager<T> getPager() {
synchronized (lock) {
if (pager == null) {
pager = new ParseQueryPager<T>(query, objectsPerPage) {
@Override
protected ParseQuery<T> createQuery(int page) {
// Workaround for backwards compatibility
ParseQuery<T> query = new ParseQuery<>(getQuery());
if (paginationEnabled) {
setPageOnQuery(page, query);
}
return query;
}
};
cts = new CancellationTokenSource();
}

return pager;
}
}

private List<T> getObjects() {
return getPager().getObjects();
}

/** {@inheritDoc} **/
@Override
public T getItem(int index) {
if (index == getPaginationCellRow()) {
return null;
}
return objects.get(index);
return getObjects().get(index);
}

/** {@inheritDoc} **/
Expand Down Expand Up @@ -337,18 +349,15 @@ public void unregisterDataSetObserver(DataSetObserver observer) {
* Remove all elements from the list.
*/
public void clear() {
objectPages.clear();
cancelAllQueries();
syncObjectsWithPages();
notifyDataSetChanged();
currentPage = 0;
}

private void cancelAllQueries() {
for (ParseQuery q : runningQueries) {
q.cancel();
synchronized (lock) {
if (cts != null) {
cts.cancel();
}
pager = null;
cts = null;
}
runningQueries.clear();

notifyDataSetChanged();
}

/**
Expand All @@ -359,118 +368,47 @@ private void cancelAllQueries() {
* {@code false}.
*/
public void loadObjects() {
loadObjects(0, true);
loadNextPage(true);
}

private void loadObjects(final int page, final boolean shouldClear) {
final ParseQuery<T> query = queryFactory.create();

if (objectsPerPage > 0 && paginationEnabled) {
setPageOnQuery(page, query);
private void loadNextPage(final boolean shouldClear) {
synchronized (lock) {
if (shouldClear && pager != null) {
cts.cancel();
pager = null;
}
}

notifyOnLoadingListeners();

// Create a new page
if (page >= objectPages.size()) {
objectPages.add(page, new ArrayList<T>());
}

// In the case of CACHE_THEN_NETWORK, two callbacks will be called. Using this flag to keep
// track of the callbacks.
final Capture<Boolean> firstCallBack = new Capture<>(true);

runningQueries.add(query);

// TODO convert to Tasks and CancellationTokens
// (depends on https://github.com/ParsePlatform/Parse-SDK-Android/issues/6)
query.findInBackground(new FindCallback<T>() {
getPager().loadNextPage(new FindCallback<T>() {
@Override
public void done(List<T> foundObjects, ParseException e) {
if (!runningQueries.contains(query)) {
public void done(List<T> results, ParseException e) {
if (results == null && e == null) { // cancelled
return;
}
// In the case of CACHE_THEN_NETWORK, two callbacks will be called. We can only remove the
// query after the second callback.
if (Parse.isLocalDatastoreEnabled() ||
(query.getCachePolicy() != CachePolicy.CACHE_THEN_NETWORK) ||
(query.getCachePolicy() == CachePolicy.CACHE_THEN_NETWORK && !firstCallBack.get())) {
runningQueries.remove(query);
}

// Backwards compatibility
if ((!Parse.isLocalDatastoreEnabled() &&
query.getCachePolicy() == CachePolicy.CACHE_ONLY) &&
query.getCachePolicy() == ParseQuery.CachePolicy.CACHE_ONLY) &&
(e != null) && e.getCode() == ParseException.CACHE_MISS) {
// no-op on cache miss
return;
}

if ((e != null) &&
((e.getCode() == ParseException.CONNECTION_FAILED) ||
(e.getCode() != ParseException.CACHE_MISS))) {
hasNextPage = true;
} else if (foundObjects != null) {
if (shouldClear && firstCallBack.get()) {
runningQueries.remove(query);
cancelAllQueries();
runningQueries.add(query); // allow 2nd callback
objectPages.clear();
objectPages.add(new ArrayList<T>());
currentPage = page;
firstCallBack.set(false);
}

// Only advance the page, this prevents second call back from CACHE_THEN_NETWORK to
// reset the page.
if (page >= currentPage) {
currentPage = page;
notifyDataSetChanged();

// since we set limit == objectsPerPage + 1
hasNextPage = (foundObjects.size() > objectsPerPage);
}

if (paginationEnabled && foundObjects.size() > objectsPerPage) {
// Remove the last object, fetched in order to tell us whether there was a "next page"
foundObjects.remove(objectsPerPage);
}

List<T> currentPage = objectPages.get(page);
currentPage.clear();
currentPage.addAll(foundObjects);

syncObjectsWithPages();

// executes on the UI thread
notifyDataSetChanged();
}

notifyOnLoadedListeners(foundObjects, e);
notifyOnLoadedListeners(results, e);
}
});
}

/**
* This is a helper function to sync the objects with objectPages. This is only used with the
* CACHE_THEN_NETWORK option.
*/
private void syncObjectsWithPages() {
objects.clear();
for (List<T> pageOfObjects : objectPages) {
objects.addAll(pageOfObjects);
}
}, cts.getToken());
}

/**
* Loads the next page of objects, appends to table, and notifies the UI that the model has
* changed.
*/
public void loadNextPage() {
if (objects.size() == 0 && runningQueries.size() == 0) {
loadObjects(0, false);
}
else {
loadObjects(currentPage + 1, false);
}
loadNextPage(false);
}

/**
Expand All @@ -482,7 +420,7 @@ public void loadNextPage() {
*/
@Override
public int getCount() {
int count = objects.size();
int count = getObjects().size();

if (shouldShowPaginationCell()) {
count++;
Expand Down Expand Up @@ -689,7 +627,7 @@ public void setAutoload(boolean autoload) {
return;
}
this.autoload = autoload;
if (this.autoload && !dataSetObservers.isEmpty() && objects.isEmpty()) {
if (this.autoload && !dataSetObservers.isEmpty() && getObjects().isEmpty()) {
loadObjects();
}
}
Expand Down Expand Up @@ -725,11 +663,12 @@ private View getDefaultView(Context context) {
}

private int getPaginationCellRow() {
return objects.size();
return getObjects().size();
}

private boolean shouldShowPaginationCell() {
return paginationEnabled && objects.size() > 0 && hasNextPage;
ParseQueryPager<T> pager = getPager();
return paginationEnabled && pager.getObjects().size() > 0 && pager.hasNextPage();
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Nit, since we have getObjects() helper method, let's just use the helper method so it is easy for us to change in the future.

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I'm going to leave it so that getObjects() and hasNextPage() are ensured to be called on the same instance of pager

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👍

}

private void notifyOnLoadingListeners() {
Expand Down
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