I am developing a Material Design Navigation Drawer. I've created a new class RecyclerItemClickListener implements RecyclerView.OnItemTouchListener in it to handle the user's click on the list items. I use the class this way within the MainActivity class' onCreate method:
mRecyclerView.addOnItemTouchListener(
new RecyclerItemClickListener(this, mRecyclerView, new RecyclerItemClickListener.OnItemClickListener() {
#Override
public void onItemClick(View view, int position) {// do whatever
if(position!=0){
setItemChecked(position, true);
setSelectable(true);
boolean isSelected = view.isSelected();
view.setActivated(isSelected);
selectItem(position);
}
}
#Override
public void onItemLongClick(View view, int position){
// ...
}
})
);
I based this code from this blog post: RecyclerView part 2 but it's not getting the job done, and to me it's not clear at all on how am I supposed to get it working.
I've also checked out this seemingly easy solution: Innodroid - Tracking Selected Item in RecyclerView (also quoted in this answer) but it's not clear on how I am supposed to derive my MyAdapter class to the TrackSelectionAdapter class.
What's the best way to highlight list items? I'm stuck.
Please help.
I think, I've found the best tutorial on how to use the RecyclerView with all functions we need and with no libraries (single+multiselection, hightlight, ripple, click and remove in multiselection, etc...). From a first look it seems well explained.
Here it is --> http://enoent.fr/blog/2015/01/18/recyclerview-basics/
[EDIT] I finally found the time to try it out and I even created my own more flexible, everybody can benefit my improvements: https://github.com/davideas/FlexibleAdapter.
In this link I also explain how it works. Please have a look and feel free to add it to your project.
Related
I'm trying to attach an onClickListener() method to an item which is inside a Recycler view. I know I can easily achive that by doing it from the RecyclerAdapter, but the goal of doing that is to show a custom dialog with some information that parent fragment contains, there are some ways to pass data, but I think that's better to attach the listener from fragment instead, and this way I can directly access the data.
I've tried to access from the fragment the way I use to do it from the adapter, with some modifications:
myRecyclerAdapter.myViewHolder.reportContainer.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getContext(),"Touch",Toast.LENGTH_SHORT).show();
}
});
But aparently the myViewHolder object it's not created yet by the time I try to use it, so I get the Java NullPointerException (F..$&##^$&^%, don't misunderstand me, I love it).
So, I need some help to do what I'm trying to, or some other good ideas to try, warning: I;m really trying to avoid passing data, except with maybe a ViewModel (don't know if I can), becouse it's a lot of fields to pass
This is fundamentally incorrect. The problem here is, there are multiple ViewHolders in the RecylerView. Which one do you want to attach it to? There would be n number of items and not all items will be rendered at the same time.
Instead of updating the ViewHolder, use a callback.
class MyAdapter extends RecyclerView.Adapter {
MyAdapterCallback callback = null;
....
#Override
public void onBindViewHolder(holder: ViewHolder, position: Int) {
holder.reportContainer.setOnClickListener { // You can set this in OnCreateViewHolder as well.
if (callback != null) {
callback.onClick();
}
}
}
}
interface MyAdapterCallback {
void onClick()
}
From your fragment,
myAdapter.callback = new MyAdapterCallback() {
#Override
public void onClick() {
// Access your fragment variables here.
}
}
I have a GridView layout that makes use of an ArrayAdapter to populate its contents. I want to make use of fast-scrolling and as such have added the following attributed to the layout XML:
android:fastScrollAlwaysVisible="true"
android:fastScrollStyle="#android:style/Widget.Material.FastScroll"
I am now able to make use of fast scrolling to navigate but would now like to add a material thumb preview as such:
From my understanding, I would have to implement the SectionIndexer interface from my ArrayAdapter as so:
class exampleArrayAdapter extends ArrayAdapter<...> implements SectionIndexer
At this point, I have reached a bump and can't figure out how to get the thumb preview and fear I may be doing something wrong. Pointers as to how I can get this working or what I should look up would be appreciated.
I have finally had time to look back at this, and the solution turns out to be very trivial! This is what I did:
#Override
public Object[] getSections() {
ArrayList<String> labels = new ArrayList<>();
for (LaunchableActivity activity: mActivityInfos) {
labels.add(activity.getActivityLabel());
}
return labels.toArray();
}
#Override
public int getPositionForSection(int i) {
return i;
}
#Override
public int getSectionForPosition(int i) {
// We do not need this
return 0;
}
I had a list of LaunchableActivity and based of that created a sections array to be returned. For my needs, all I required was to implement getPositionForSection and not getSectionForPosition. Your use case may vary.
The source code where I implemented this is available here, specifically on commits:
a2c9ddd1c647919afbf24262ac1a7772a08e468c
08802e17f4c75835c28232353fed68964f5d7746
0d73a788c6b92d7b9c05a2871778da42af02afd8
f13a59f02690481801bd07ffc593648b8e71d036
This is my situation:
I would like the list to treat the "header" and tabs sections as a list header so that the "header" and tabs do not stay fixed on the screen and they all scroll together with the list.
I can't simply add the header and tabs as a headerView for the list via mListView.addHeaderView() because the tabs will swap out the "List" content area when pressed. The content area for the other tabs will contain other lists, and the header and tabs should scroll with the new list as well.
I'd appreciate any help.
You can override the getViewType method in order to precise how many kind of rows you listview has.
Have a look here.
Think of the entire thing as the ListView. You can call addHeaderView() as many times as you want so you can have two header views ("Header", and "Tab | Tab | Tab").
Re:
I can't simply add the header and tabs as a headerView for the list via mListView.addHeaderView() because the tabs will swap out the "List" content area when pressed.
Yes you can.
Update the reference to your list data and call mAdapter.notifyDataSetChanged().
I had the same need as you, I found this project that implements exactly what you need, plus some more eye-candy tricks.
https://github.com/kmshack/Android-ParallaxHeaderViewPager
The magic is binding the scrolling that happens in the fragment list to the header defined in the activity. There is also a fundamental binding between the selection of a tab and the scroll position in the list, to adjust lists when swiping.
This code is based upon that github repo but is simpler (therefore less robust), read it just to understand what happens, then read the source in the repo.
public class MyFragment extends Fragment implements OnScrollListener {
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
((MyParentActivity) getActivity()).onScrollFragment(view, mTabPosition);
}
public void adjustScroll(int scrollHeight) {
if (scrollHeight == 0 && fragmentListView.getFirstVisiblePosition() >= 1) {
return;
}
officesListView.setSelectionFromTop(1, scrollHeight);
}
}
then in the activity you just need these two specific methods
public class MyParentActivity implements ViewPager.OnPageChangeListener{
#Override
public void onPageSelected(int position)
myFragmentPagerAdapter.getFragmentAt(position)
.adjustScroll((int) (mHeader.getHeight() + ViewHelper.getTranslationY(mHeader)));
}
public void onScrollFragment(AbsListView view, int tabPosition) {
if (mViewPager.getCurrentItem() == tabPosition) {
int scrollY = getScrollY(view);
ViewHelper.setTranslationY(mHeader, Math.max(-scrollY, mMinHeaderTranslation));
}
}
}
this code is good up to API 8 thanks to NineOldAndroids' ViewHelper
I'm using a FragmentStatePagerAdapter with a ViewPager.
Everything is working fine. If I open my activity with an empty Adapter, the ViewPageris empty, if I add items, the ViewPager updates correctly.
BUT, if I open my activity and delete the last item of my ViewPager, the ViewPagerdoes not invalidate correctly and keeps the last Fragment visible.
How can I avoid this?
I'm using my library, it's a wrapper class for ViewPager + ViewPagerIndicator + FragmentPager(State)Adapter:
The class itself is placed here: https://github.com/MichaelFlisar/PagerManager/blob/master/src/com/michaelflisar/pagermanager/MFragmentPagerStateAdapter.java
The implementation is placed here: https://github.com/MichaelFlisar/PagerManager/blob/master/src/com/michaelflisar/pagermanager/MPagerAdapterHelper.java
It implements a simple FragmentStatePagerAdapter with weak references to it's fragments...
My code looks like following:
mPagerManager = new MPagerManager<ExerciseViewFragment, MFragmentPagerStateAdapter<ExerciseViewFragment>>(pager, tpi,
new MFragmentPagerStateAdapter<ExerciseViewFragment>(fragmentManager)
{
#Override
public CharSequence getPageTitle(int pos)
{
return mData.workout.getWExercise().get(pos).getExercise().getName();
}
#Override
public int getCount()
{
return mData.workout.getWExercise().size();
}
#Override
public ExerciseViewFragment createFragment(int pos)
{
return ExerciseViewFragment.newInstance(pos, mData.workout.getWExercise());
}
});
I'm calling mPagerManager.notifyDataSetChanged(); which forwards the call to the FragmentPagerStateAdapter directly...
PS: I know, I can make it invisible, if item count is 0... But I'm wondering if there's a better solution
This is an old question but I thought you might still need to know what to do. It's very common issue. ViewPager does not invalid views which are already created(including these which are ready on the left and right side of your current view).
Solving this is very easy. Just implement the following method in your adapter like this:
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
By default this method returns PagerAdapter.POSITION_UNCHANGED.
For most developers this method usage is misleading, I had this problem myself till I realised that this method is used by ViewPager.dataSetChanged() to establish which items should be recreated. With above code you tell ViewPager to recreate all items whenever data set change.
I've implemented a gridview and I've been hacking it together from examples to get a feel for how it works. I created and Adapter and when I came to implement the listener I discovered it is achieved like this.
private OnItemClickListener mColourClickListener = new OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> parent, View v, int position, long id){
Log.d("LISTENER","Position Clicked ["+position+"]");
}
};
Why is this different to a listview and why does it have it's methods implemented in braces after the variable declaration?
Many thanks,
M
You are creating new instance of anonymous class that implements OnItemClickListener interface. It is easier than defining new class and then creating new instance of this class. Anonymous class allows you to define class inline where you need it. Listeners are usually for one time use, so they are often defined as anonymous classes.