I want to implement search functionality for my RecyclerView. On text changed i want to change the data that are displayed with this widget. Maybe this question has been asked before or is simple, but I don't know how the change the data that is to be shown...
My RecyclerView is defined as follows:
// 1. get a reference to recyclerView mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView); // 2. set layoutManger mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); // 3. create an adapter mAdapter = new ItemsAdapter(itemsData); // 4. set adapter mRecyclerView.setAdapter(mAdapter);
And the data that I am showing is something like:
ItemData itemsData[] = { new ItemData("Mary Richards"), new ItemData("Tom Brown"), new ItemData("Lucy London") };
So when when I want to give the adapter another set of data, another array (with one item for example), what should I do?
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project. Step 2 − Open build. gradle and add Recycler view & Card view library dependencies. Step 3 − Add the following code to res/layout/activity_main.
A ViewHolder describes an item view and metadata about its place within the RecyclerView. RecyclerView. Adapter implementations should subclass ViewHolder and add fields for caching potentially expensive View.
RecyclerView is the ViewGroup that contains the views corresponding to your data. It's a view itself, so you add RecyclerView into your layout the way you would add any other UI element. Each individual element in the list is defined by a view holder object.
notifyItemChanged. Notify any registered observers that the item at position has changed with an optional payload object. This is an item change event, not a structural change event. It indicates that any reflection of the data at position is out of date and should be updated.
If you have stable ids in your adapter, you can get pretty good results (animations) if you create a new array containing the filtered items and call
recyclerView.swapAdapter(newAdapter, false);
Using swapAdapter hints RecyclerView that it can re-use view holders. (vs in setAdapter, it has to recycle all views and re-create because it does not know that the new adapter has the same ViewHolder set with the old adapter).
A better approach would be finding which items are removed and calling notifyItemRemoved(index)
. Don't forget to actually remove the item. This will let RecyclerView run predictive animations. Assuming you have an Adapter that internally uses an ArrayList, implementation would look like this:
// adapter code final List<ItemData> mItems = new ArrayList(); //contains your items public void filterOut(String filter) { final int size = mItems.size(); for(int i = size - 1; i>= 0; i--) { if (mItems.get(i).test(filter) == false) { mItems.remove(i); notifyItemRemoved(i); } } }
It would perform even better if you can batch notifyItemRemoved
calls and use notifyItemRangeRemoved
instead. It would look sth like: (not tested)
public void filterOut(String filter) { final int size = mItems.size(); int batchCount = 0; // continuous # of items that are being removed for(int i = size - 1; i>= 0; i--) { if (mItems.get(i).test(filter) == false) { mItems.remove(i); batchCount ++; } else if (batchCount != 0) { // dispatch batch notifyItemRangeRemoved(i + 1, batchCount); batchCount = 0; } } // notify for remaining if (batchCount != 0) { // dispatch remaining notifyItemRangeRemoved(0, batchCount); } }
You need to extend this code to add items that were previously filtered out but now should be visible (e.g. user deletes the filter query) but I think this one should give the basic idea.
Keep in mind that, each notify item call affects the ones after it (which is why I'm traversing the list from end to avoid it). Traversing from end also helps ArrayList's remove method performance (less items to shift).
For example, if you were traversing the list from the beginning and remove the first two items. You should either call
notifyItemRangeRemoved(0, 2); // 2 items starting from index 0
or if you dispatch them one by one
notifyItemRemoved(0); notifyItemRemoved(0);//because after the previous one is removed, this item is at position 0
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