I got 3 types of items I want to add to my RecyclerView, a button (item with a button inside of it), a dummy (item with empty display), a normal item (item with some stuff inside of it).
I'm going to write a scenario that describes the adding/remove process when it should work but it isn't for some reason.
Scenario:
-add a button + dummy to RecyclerView, they get displayed just fine.
WidgetItem dummy = new WidgetItem(true);
arrayList.add(0, dummy);
ca.notifyItemInserted(0);//ca is my adapter
WidgetItem btnHolder = new WidgetItem();
btnHolder.setButton(true);
arrayList.add(0, btnHolder);
ca.notifyItemInserted(0);
-add another normal item + 2 dummies -->fine
if (nbrItems % 3 == 0) {
for (int i = 0; i < 2; i++) {
WidgetItem dummy = new WidgetItem(true);
dummy.setTilte("dummy" + i);
arrayList.add(0, dummy);
ca.notifyItemInserted(0);
}
}
arrayList.add(0, wItem);
ca.notifyItemInserted(0);
-remove 1 dummy + add a normal item -->fine
if ((nbrDummy == 3)||(nbrDummy == 2))
for (int i = 0; !foundDummy; i++) {
if (cii.get(i).getDummy()) {
arrayList.remove(i);
ca.notifyItemRemoved(i);
foundDummy = true;
}
}
arrayList.add(0, wItem);
ca.notifyItemInserted(0);
-remove 1 dummy + add a normal item (the same as above) -->not fine
This's when the problem happens and instead of getting a 3rd 'normal item' i get another dummy instead in the display.
What confused me was that the "onCreateViewHolder" method in my custom adapter didn't even get called at this step while it got called just fine in the previous ones.
Even if the item that just got displayed was a dummy the "onCreateViewHolder" method should execute at least like how it should.
But the code just skipped right to the "onBindViewHolder" method.
I'm suspecting that maybe something happened after the deletion of that dummy but then again why it worked fine in the code above.
I tried "notifyItemRangeChanged" after deleting the dummy but the whole recyclerView got messed up.
So yeah, what's going on here?
My problem was due to how RecyclerView works I suppose.
After I delete an item from the list and create another, the same old back item that I deleted come back instead.
So after trying a couple of things i found out that putting recyclerView.getRecycledViewPool().clear(); between the items deletion and the creation code solved my problem.
Related
I was designing an Instagram story type template. I am stuck at a very weird problem. I have used recycler view in the main activity.
MainActivity: (This is just the layout shown. I have change the orientation to Horizontal).
My layout:
Then I have designed a custom adapter and in the layout I have used a linearLayout. When clicked on each view It opens a new Activity which shows the whole story content.
Just like in Instagram when a user opens any story, the user can click on the right side of the screen to get to the next story, or left of the screen to get to the previous one. I tried to implement this same functionality. Opening the story was implemented successfully. The problem comes when I added the functionality of right and left click on the screen. I added two button; one to the right and one to the left. The problem is like, if there are currently 3 views visible, then I can navigate in between these stories only and not to the stories which are not visible in the screen because of the recycler view.
The below code is for right and left clicks
leftArrow = findViewById(R.id.leftArrow);
leftArrow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(myAdapter.currentPosition - 1 >= 0) {
int firstVis = MainActivity.linearLayoutManager.findFirstVisibleItemPosition();
MainActivity.linearLayoutManager.scrollToPosition(firstVis - 1);
rightOrLeftClicks(myAdapter.currentPosition - 1);
}
}
});
rightArrow = findViewById(R.id.rightArrow);
rightArrow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(myAdapter.currentPosition + 1 < myAdapter.localDataSet.length) {
int lastVis = MainActivity.linearLayoutManager.findLastVisibleItemPosition();
MainActivity.linearLayoutManager.scrollToPosition(lastVis + 1);
rightOrLeftClicks(myAdapter.currentPosition + 1);
}
}
});
}
Below code is of the function rightOrLeftClicks
public void rightOrLeftClicks(int position) {
finish();
Log.d("rl", "working");
nextView = MainActivity.linearLayoutManager.getChildAt(position);
Log.d("ll", "The last element is " + MainActivity.linearLayoutManager.findLastVisibleItemPosition());
if(nextView != null)myAdapter.onClickView(position, myAdapter.localDataSet[position].symptom, nextView);
}
Below code is for onClickView, It is same code for clicking any view (Story) or clicking the right or left buttons. Basically I just opened the another activity by passing an intent with the next or previous view I obtained when clicked on right or left respectively.
public static void onClickView(int position, String element, View v) {
Intent intent = new Intent(v.getContext(), MainActivity2.class);
idPosition = "";
idPosition = element;
ArrayList<String> passingContent = new ArrayList<>();
currentPosition = position;
passingContent.add(localDataSet[position].description);
passingContent.add(localDataSet[position].imageUrl);
intent.putExtra(element + "", passingContent);
v.getContext().startActivity(intent);
}
The problem is it only gives the visible views to me. Not the rest of the views. I tried auto scrolling so that the next or the previous view become visible but it doesn't seems to work. The last visible position of the child remains the same and it return a null view to me when I try to open the view just after the last visible view.
Assume there are 5 stories. Then I will see only 3 stories in the screen the rest can be seen by scrolling. When I click any of the stories. I can only navigate between 1,2 and 3. When I try to click right from story 3 to see the story 4. The current story is killed by finish() function and null is returned in the nextView variable because of which the story 4 is not loaded and I am returned to the MainActivity.
I have to navigate to all stories present in my recycler view.
Do these changes may help:
1/
I think you should use ViewPager. It automatically snaps to the item without scrollTo to index. Or keep using RecyclerView with the help of SnapHelper
2/
Modify onClickView method not to be static, and don't need View v to work. I see you just need View v just for the context. Why not just pass the context to that method. It's not proper to use a parameter like that, and that approach traps you into 3/ problem.
3/
nextView = MainActivity.linearLayoutManager.getChildAt(position);
You already know how RecyclerView works, just avoid using getChildAt because in some cases, the child you want hasn't been created yet. Base on your code, I think you don't even need to get the nextView
As told by Tam Huynh. The 1st point helped me in getting the new views in the linear layout. The views were working the fine.
There was a problem in the parameter of the function getChildAt. I have to pass the same position I was in previously. Because relatively the position(index) will not change for the child views.
index 0 -> story number 1
index 1 -> story number 2
index 2 -> story number 3
Like if there were story number 1,2 and 3 visible, the index 0 will contain 1st story, index 1 will contain 2nd and index 2 will contain 3rd story. when user clicked the right button on the 3rd story. The 4th story is first visible and now the screen have 2,3 and 4 visible. but the index of the 4th story will remain 3rd only. As now indexing will be like
index 0 -> story number 2
index 1 -> story number 3
index 2 -> story number 4
So, instead of passing position as parameter, currentPosition should be passed in getChildAt
I made a note card program that can help you study with JavaFX. It saves the class through XML and on boot up, it finds the XML files and adds them to an ArrayList called allProjects of type NoteCardSet, an ArrayList of NoteCards. With this, I made a dynamic amount of buttons that puts them 4 columns wide. Here is the code for that:
int amountPerRow = 4;
int current = 0;
int row = 0;
for (NoteCardSet noteCardSet : allProjects) {
Button b = new Button(noteCardSet.getName());
GridPane.setConstraints(b, current, row);
centerMenu.getChildren().add(b);
b.setOnAction(e -> {
border.setCenter(noteCardSetLayout(noteCardSet));
});
if (current < amountPerRow - 1)
{
current++;
}
else if (current >= amountPerRow - 1)
{
current = 0;
row++;
}
}
Obviously this is creatable in JavaFX but is it possible to created this in FXML?
No you cannot do this in FXML. There is no way to write a LOOP in fxml. If you are just considered about a Button, then you may use SceneBuilder and drag-drop multiple buttons.
Though, if you are considered about a more complex UI and want to repeat them, you can create a separate FXML and include it as many time as you need using <fx:include>.
You can also load the same fxml multiple times using a loop and put all the concerned data inside the initialize(), but this might not be the best solution you are looking for.
Looking for a GWT DataGrid component which implements infinite scroll, BUT also makes sure to discard the results no longer visible on the screen : such as the previously loaded results that are not shown anymore.
This is to avoid a memory hog.
I've been trying to find this on Google, but no luck so far.
Please note : I could take a JS library and adapt it to what I need, but I don't think it would work good with GWT's DataGrid component.
Edit: I am interested specifically in an infinite scroll which ALSO discards/releases the topmost results that are not visible (and loads them up as appropriate).
Any ideas ?
As a matter of fact the showcase example has an infinite scrolling CellList. (you can find the code there).
Although this was done with a CellList the same principles should also apply to a DataGrid.
Check out the ShowMorePagerPanel.java file.
Update:
The onScroll function of ShowMorePagerPanel.java will add the new records at the bottom. However you can easily change the behavior:
Something along the lines (not tested tough):
HasRows display = getDisplay();
if (display == null) {
return;
}
boolean loadData = false;
// If scrolling up, change newStart
int oldScrollPos = lastScrollPos;
lastScrollPos = scrollable.getVerticalScrollPosition();
// get the current visible Range
Range currentRange = display.getVisibleRange();
if (oldScrollPos >= lastScrollPos) {
int newStart = Math.max(
currentRange.getStart() - incrementSize,0);
loadData = true;
}
int maxScrollTop = scrollable.getWidget().getOffsetHeight()
- scrollable.getOffsetHeight();
if (lastScrollPos >= maxScrollTop) {
// We are near the end, so increase the page size.
int newPageSize = Math.min(
display.getVisibleRange().getLength() + incrementSize,
display.getRowCount());
loadData = true;
}
if (loadData) {
display.setVisibleRange(newStart, newPageSize);
}
Currently the list when populated is starting with the view # the bottom of the list. Is there a way using listAdapters to force it to the top of the list?
Currently the orientation scrolls to the bottom on create. Is there a way to pin the screen to the top when it creates? http://imgur.com/wGTEy in this example you see that entry 1 on create is shoved upwards to make room for six... Instead I want it to populate like this. http://imgur.com/6Lg6e... entry 1 is the top of the list and 6 is pushed off to the bottom for the scroll.
If you look at the picture above you will notice it starts at the bottom of the list instead of at the top. Any Ideas?
mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mStrings);
setListAdapter(mAdapter);
registerForContextMenu(getListView());
populateFields();
private void populateFields() {
if (mRowId != null) {
Cursor note = mDbHelper.fetchDaily(mRowId);
startManagingCursor(note);
String body = note.getString(note.getColumnIndexOrThrow(NotesDbAdapter.KEY_DBODY));
mAdapter.clear();
if (!(body.trim().equals(""))){
String bodysplit[] = body.split(",");
for (int i = 0; i < bodysplit.length; i++) {
mAdapter.add(bodysplit[i].trim());
}
}
}
}
**edited to fix != string error.
You want the items later in the list to be at the top of the ListView? If so, check out this questions: Is it possible to make a ListView populate from the bottom?
You are completely changing the adapter, so the scroll position is lost in the process... You can use:
ListView listView = getListView();
int position = listView.getFirstVisiblePosition();
if (!(body.trim().equals(""))){
String bodysplit[] = body.split(",");
for (int i = 0; i < bodysplit.length; i++) {
mAdapter.add(bodysplit[i].trim());
}
}
listView.setSelection(position);
But this is not perfect as it is, if a row is added before position the index will be off. If your list contains unique values you can use ArrayAdapter#getPosition(), to find the new index.
While I still recommend using a CursorAdapter, because it handles large table data better, I want to address a point on efficiency with your ArrayAdapter code.
By using adapter.clear() and adapter.add() you are asking the ListView to redraw itself on every step... potentially dozens or hundreds of times. Instead you should work with the ArrayList directly and then ask the ListView to redraw once itself with ArrayAdapter#notifyDataSetChanged() after the loop completes.
I got a doubt regarding pre-selecting(setSelectedIndex(index)) an item in a ListBox, Im using Spring + GWT.
I got a dialog that contains a panel, this panel has a FlexPanel, in which I've put a couple ListBox, this are filled up with data from my database.
But this Panel is for updates of an entity in my database, thus I wanted it to pre-select the current properties for this items, allowing the user to change at will.
I do the filling up in the update method of the widget.
I tried setting the selectedItem in the update method, but it gives me an null error.
I've searched a few places and it seems that the ListBox are only filled at the exact moment of the display. Thus pre-selecting would be impossible.
I thought about some event, that is fired when the page is displayed.
onLoad() doesnt work..
Anyone have something to help me out in here?
I really think you can set the selection before it's attached and displayed, but you have to have added the data before you can select an index. If this is a single select box you could write something like this:
void updateListContent(MyDataObject selected, List<MyDataObject> list){
for (MyDataObject anObject : list) {
theListBox.addItem(anObject.getTextToDisplay(), anObject.getKeyValueForList());
}
theListBox.setSelectedIndex(list.indexOf(selected));
}
If this is a multiple select box something like this may work:
void updateListContent(List<MyDataObject> allSelected, List<MyDataObject> list){
for (MyDataObject anObject : list) {
theMultipleListBox.addItem(anObject.getTextToDisplay(), anObject.getKeyValueForList());
}
for (MyDataObject selected : allSelected) {
theMultipleListBox.setItemSelected(list.indexOf(selected), true);
}
}
(Note I haven't actually compiled this, so there might be typos. And this assumes that the selected element(s) is really present in the list of possible values, so if you cant be sure of this you'll need to add some bounds checking.)
I've been happily setting both the values and the selection index prior to attachment so as far as I'm aware it should work. There's a bug however when setting the selected index to -1 on IE, see http://code.google.com/p/google-web-toolkit/issues/detail?id=2689.
private void setSelectedValue(ListBox lBox, String str) {
String text = str;
int indexToFind = -1;
for (int i = 0; i < lBox.getItemCount(); i++) {
if (lBox.getValue(i).equals(text)) {
indexToFind = i;
break;
}
}
lBox.setSelectedIndex(indexToFind);
}
Pre-selection should work also with setValue()-function. Thus, no complicated code is needed.