This library allows you to implement Google Photos style multi-selection in your apps! You start by long pressing an item in your list, then you drag your finger without letting go to select more.
You can download a sample APK or view it on Google Play!
Add this in your root build.gradle file (not your module build.gradle file):
allprojects {
repositories {
...
maven { url "https://jitpack.io" }
}
}Add the following to your module's build.gradle file:
dependencies {
// ...
compile('com.github.afollestad:drag-select-recyclerview:0.3.1@aar') {
transitive = true
}
}- Introduction
- DragSelectRecyclerView
- How to create a DragSelectRecyclerView in your layout. How to set it up from code.
- DragSelectRecyclerViewAdapter
- An example of how adapter's should be setup. Goes over how to know which items are selected, how to prevent certain items from being selected, etc.
- User Activation, Initializing Drag Selection
- How drag selection mode is activated by a long press. How to maintain selected items through configuration changes, etc.
- Selection Retrieval and Modification
- How to retrieve selected indices and modify them.
- Auto Scroll
- By default, this library will auto-scroll up or down if the user holds their finger at the top or bottom of the list during selection mode.
DragSelectRecyclerView and DragSelectRecyclerViewAdapter are the two main classes of this library.
They work together to provide the functionality you seek.
This library will also automatically auto scroll like Google Photos. If you drag to the top of the RecyclerView, the list will scroll up, and vice versa.
DragSelectRecyclerView replaces the regular RecyclerView in your layouts. It intercepts touch events
when you tell if selection mode is active, and automatically reports to your adapter.
<com.afollestad.dragselectrecyclerview.DragSelectRecyclerView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />Setup is basically the same as it would be for a regular RecyclerView. You just set a LayoutManager
and RecyclerView.Adapter to it:
DragSelectRecyclerView list = (DragSelectRecyclerView) findViewById(R.id.list);
list.setLayoutManager(new GridLayoutManager(this, 3));
list.setAdapter(adapter);The only major difference here is what you need to pass inside of setAdapter(). It cannot be any
regular RecyclerView.Adapter, it has to be a sub-class of DragSelectRecyclerViewAdapter which
is discussed below.
DragSelectRecyclerViewAdapter is a RecyclerView.Adapter sub-class that DragSelectRecyclerView is
able to communicate with. It keeps track of selected indices – and it allows you to change them, clear them,
listen for changes, and check if a certain index is selected.
A basic adapter implementation looks like this:
public class MainAdapter extends DragSelectRecyclerViewAdapter<MainAdapter.MainViewHolder> {
public interface ClickListener {
void onClick(int index);
void onLongClick(int index);
}
private final ClickListener mCallback;
// Constructor takes click listener callback
protected MainAdapter(ClickListener callback) {
super();
mCallback = callback;
}
@Override
public MainViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.griditem_main, parent, false);
return new MainViewHolder(v);
}
@Override
public void onBindViewHolder(MainViewHolder holder, int position) {
super.onBindViewHolder(holder, position); // this line is important!
// Sets position + 1 to a label view
holder.label.setText(String.format("%d", position + 1));
if (isIndexSelected(position)) {
// Item is selected, change it somehow
} else {
// Item is not selected, reset it to a non-selected state
}
}
@Override
protected boolean isIndexSelectable(int index) {
// This method is OPTIONAL, returning false will prevent the item at the specified index from being selected.
// Both initial selection, and drag selection.
return true;
}
@Override
public int getItemCount() {
return 60;
}
public class MainViewHolder extends RecyclerView.ViewHolder
implements View.OnClickListener, View.OnLongClickListener{
public final TextView label;
public MainViewHolder(View itemView) {
super(itemView);
this.label = (TextView) itemView.findViewById(R.id.label);
this.itemView.setOnClickListener(this);
this.itemView.setOnLongClickListener(this);
}
@Override
public void onClick(View v) {
// Forwards to the adapter's constructor callback
if (mCallback != null) mCallback.onClick(getAdapterPosition());
}
@Override
public boolean onLongClick(View v) {
// Forwards to the adapter's constructor callback
if (mCallback != null) mCallback.onLongClick(getAdapterPosition());
return true;
}
}
}You choose what to do when an item is selected (in onBindViewHolder). isIndexSelected(int) returns
true or false. The click listener implementation used here will aid in the next section.
The library won't start selection mode unless you tell it to. You want the user to be able to active it. The click listener implementation setup in the adapter above will help with this.
public class MainActivity extends AppCompatActivity implements
MainAdapter.ClickListener, DragSelectRecyclerViewAdapter.SelectionListener {
private DragSelectRecyclerView mList;
private MainAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Setup adapter and callbacks
mAdapter = new MainAdapter(this);
// Receives selection updates, recommended to set before restoreInstanceState() so initial reselection is received
mAdapter.setSelectionListener(this);
// Restore selected indices after Activity recreation
mAdapter.restoreInstanceState(savedInstanceState);
// Setup the RecyclerView
mList = (DragSelectRecyclerView) findViewById(R.id.list);
mList.setLayoutManager(new GridLayoutManager(this, getResources().getInteger(R.integer.grid_width)));
mList.setAdapter(mAdapter);
}
@Override
public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
super.onSaveInstanceState(outState, outPersistentState);
// Save selected indices to be restored after recreation
mAdapter.saveInstanceState(outState);
}
@Override
public void onClick(int index) {
// Single click will select or deselect an item
mAdapter.toggleSelected(index);
}
@Override
public void onLongClick(int index) {
// Long click initializes drag selection, and selects the initial item
mList.setDragSelectActive(true, index);
}
@Override
public void onDragSelectionChanged(int count) {
// TODO Selection was changed, updating an indicator, e.g. a Toolbar or contextual action bar
}
}DragSelectRecyclerViewAdapter contains many methods to help you!
// Clears all selected indices
adapter.clearSelected();
// Sets an index as selected (true) or unselected (false);
adapter.setSelected(index, true);
// If an index is selected, unselect it. Otherwise select it. Returns new selection state.
boolean selectedNow = adapter.toggleSelected(index);
// Gets the number of selected indices
int count = adapter.getSelectedCount();
// Gets all selected indices
Integer[] selectedItems = adapter.getSelectedIndices();
// Checks if an index is selected, useful in adapter subclass
boolean selected = adapter.isIndexSelected(index);
// Sets a listener that's notified of selection changes, used in the section above
adapter.setSelectionListener(listener);
// Used in section above, saves selected indices to Bundle
adapter.saveInstanceState(outState);
// Used in section above, restores selected indices from Bundle
adapter.restoreInstanceState(inState);By default, this library will auto scroll. During drag selection, moving your finger to the top of the list will scroll up. Moving your finger to the bottom of the list will scroll down.
At the start of the activation point at the top or bottom, the list will scroll slowly. The further you move into the activation area, the faster it will scroll.
You can disable auto scroll, or change the activation hotspot from your layout XML:
<com.afollestad.dragselectrecyclerview.DragSelectRecyclerView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
app:dsrv_autoScrollEnabled="true"
app:dsrv_autoScrollHotspotHeight="56dp" />56dp is the default hotspot height, you can raise or lower it if necessary. Smaller hotspots will scroll quickly since there's not much room for velocity change.