GWT CellBrowser- how to always show all values? - gwt

GWT's CellBrowser is a great way of presenting dynamic data.
However when the browser contains more rows than some (seemingly) arbitrary maximum, it offers a "Show More" label that the user can click to fetch the unseen rows.
How can I disable this behavior, and force it to always show every row?

There are several ways of getting rid of the "Show More" (which you can combine):
In your TreeViewModel, in your NodeInfo's setDisplay or in the DataProvider your give to the DefaultNodeInfo, in onRangeChange: overwrite the display's visible range to the size of your data.
Extend CellBrowser and override its createPager method to return null. It won't change the list's page size though, but you can set it to some very high value there too.

The below CellBrowser removes the "Show More" text plus loads all available elements without paging.
public class ShowAllElementsCellBrowser extends CellBrowser {
public ShowAllElementsCellBrowser(TreeViewModel viewModel, CellBrowser.Resources resources) {
super(viewModel, null, resources);
}
#Override
protected <C> Widget createPager(HasData<C> display) {
PageSizePager pager = new PageSizePager(Integer.MAX_VALUE);
// removes the text "Show More" during loading
display.setRowCount(0);
// increase the visible range so that no one ever needs to page
display.setVisibleRange(0, Integer.MAX_VALUE);
pager.setDisplay(display);
return pager;
}
}

I found a valid and simple solution in setting page size to the CellBrowser's builder.
Hope this will help.
CellBrowser.Builder<AClass> cellBuilder = new CellBrowser.Builder<AClass>(myModel, null);
cellBuilder.pageSize(Integer.MAX_VALUE);
cellBrowser = cellBuilder.build();

The easiest way to do this is by using the:
cellTree.setDefaultNodeSize(Integer.MAX_VALUE);
method on your Cell Tree. You must do this before you begin expanding the tree.

My workaround is to navigate through elements of treeview dom to get "show more" element with
public static List<Element> findElements(Element element) {
ArrayList<Element> result = new ArrayList<Element>();
findShowMore(result, element); return result; }
private static void findShowMore(ArrayList res, Element element) {
String c;
if (element == null) { return; }
if (element.getInnerText().equals("Show more")) { res.add(element);
}
for (int i = 0; i < DOM.getChildCount(element); i++) { Element
child = DOM.getChild(element, i); findShowMore(res, child); } }
and than use:
if (show) { element.getStyle().clearDisplay(); } else {
element.getStyle().setDisplay(Display.NONE); }

Related

Dynamically add widgets in a cell to represent "tags" in Datagrid

In a GWT web app, I am using a DataGrid to manage elements from a database. I represent a list of elements as rows, the columns being editable fields of their characteristics (id, name, description). I am mostly using the EditTextCell class.
I now want to create a custom cell, for a column that has to represent a list of "tags" that can be attached to every element. From this cell, tags could be added, using a + button (that makes a drop-down menu appear or something), and deleted. Each tag should be a kind of button, or interactive widget (I later want to display pop-up with info, trigger actions, etc).
Actually, it would not be so different from the "tags" bar on the Stack Overflow website...
So I have been looking for a solution:
I thought this would be easy to do. I imagined just putting a FlowPanel in the cell, adding/removing Buttons/Widgets dynamically. But it turns out that in GWT Widgets and Cells and very different objects apparently..
I read making use of the AbstractCell class to create a custom cell allows to do anything, but its working is very low level and obscure to me.
I saw that CompositeCell allows to combine various cell widgets into one cell, but I have not found if it is possible to do it dynamically, or if the widgets are going to be the same for all lines throughout a column. I mostly saw examples about, for instance, how to put two Buttons in every cell of a single column.
What is the easiest way to implement what I need?
EDIT:
So, after some tests, I am going for Andrei's suggestion and going "low-level", creating a custom cell extending AbstractCell<>. I could create an appropriate "render" function, that generates a list of html "button", and also attaches Javascript calls to my Java functions when triggering a Javascript event (onclick, onmouseover, onmouseout...).
It is working pretty well. For instance, by clicking the "+" button at the end a tag list, it calls a MenuBar widget that presents the list of tags that can be added.
But I am struggling to find a way to update the underlying data when adding a tag.
To sum up:
I have a CustomData class that represents the data I want to display in each line of the table. It also contains the list of tags as a Set.
ModelTable (extends DataGrid) is my table.
CustomCell (extends AbstractCell) can renders the list of tags as several buttons on a line.
A click on a "+" button in a cell makes a AddTagMenu popup drop down, from which I can click on the tag to add.
How do I update the content of the cell?
I tried playing around with onBrowserEvent, onEnterKeyDown, bus events... with no success. At best I can indeed add a tag element to the underlying object, but the table is not updated.
It's not possible to meet your requirements without going really "low-level", as you call it.
It's relatively easy to create a cell that would render tags exactly as you want them. Plus icon is also easy, if this is the only action on the cell. However, it is very difficult to make every tag within a cell an interactive widget, because the DataGrid will not let you attach handlers to HTML rendered within a cell. You will need to supply your own IDs to these widgets, and then attach handlers to them in your code. The problem, however, is that when the DataGrid refreshes/re-renders, your handlers will most likely be lost. So you will have to attach them again to every tag in every cell on every change in the DataGrid.
A much simpler approach is to create a composite widget that represents a "row", and then add these "rows" to a FlowPanel. You can easily make it look like a table with CSS, and supply your own widget that looks like a table header. You will need to recreate some of the functionality of the DataGrid, e.g. sorting when clicked on "column" header - if you need this functionality, of course.
As you have already noted, using CompositeCell could be a way to get what you want.
The idea is to create a cell for every tag and then (during rendering) decide which one should be shown (rendered). Finally combine all those cells into one by creating a CompositeCell.
The main disadvantage of this solution is that you need to know all possible tags before you create a DataGrid.
So, if you have a fixed list of possible tags or can get a list of all existing tags and this list is reasonably small, here is a solution.
First, we need to know which tag is represented by a column so I extended a Column class to keep information about a tag. Please, note that TagColumn uses ButtonCell and also handles update when the button is clicked:
public class TagColumn extends Column<DataType, String> {
private TagEnum tag;
public TagColumn(TagEnum tag) {
super(new ButtonCell());
this.tag = tag;
setFieldUpdater(new FieldUpdater<DataType, String>() {
#Override
public void update(int index, DataType object, String value) {
Window.alert("Tag " + getTag().getName() + " clicked");
}
});
}
public TagEnum getTag() {
return tag;
}
#Override
public String getValue(DataType object) {
return tag.getName();
}
}
Then create a cell for each tag (I have hard-coded all tags in a TagEnum):
List<HasCell<DataType, ?>> tagColumns = new ArrayList<HasCell<DataType, ?>>();
for(TagEnum tag : TagEnum.values())
tagColumns.add(new TagColumn(tag));
Now, the most important part: decide either to show the tag or not - overwrite render method of the CompositeCell:
CompositeCell<DataType> tagsCell = new CompositeCell<DataType>(tagColumns) {
#Override
protected <X> void render(Context context, DataType value, SafeHtmlBuilder sb, HasCell<DataType, X> hasCell) {
if(value.getTagList().contains(((TagColumn) hasCell).getTag()))
super.render(context, value, sb, hasCell);
else
sb.appendHtmlConstant("<span></span>");
}
};
This is important to always render any element (for example empty span when the tag should not be shown). Otherwise the CompositeCell's implemantation will get confused when accessing sibling elements.
Finally, full, working example code:
private DataGrid<DataType> getGrid() {
DataGrid<DataType> grid = new DataGrid<DataType>();
List<HasCell<DataType, ?>> tagColumns = new ArrayList<HasCell<DataType, ?>>();
for(TagEnum tag : TagEnum.values())
tagColumns.add(new TagColumn(tag));
CompositeCell<DataType> tagsCell = new CompositeCell<DataType>(tagColumns) {
#Override
protected <X> void render(Context context, DataType value, SafeHtmlBuilder sb, HasCell<DataType, X> hasCell) {
if(value.getTagList().contains(((TagColumn) hasCell).getTag()))
super.render(context, value, sb, hasCell);
else
sb.appendHtmlConstant("<span></span>");
}
};
Column<DataType, DataType> tagsColumn = new Column<DataType, DataType>(tagsCell) {
#Override
public DataType getValue(DataType object) {
return object;
}
};
grid.addColumn(tagsColumn, "Tags");
grid.setRowData(Arrays.asList(
new DataType(Arrays.asList(TagEnum.gwt)),
new DataType(Arrays.asList(TagEnum.table, TagEnum.datagrid)),
new DataType(Arrays.asList(TagEnum.datagrid, TagEnum.widget, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.table, TagEnum.widget, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.table, TagEnum.datagrid, TagEnum.widget, TagEnum.customCell))
)
);
return grid;
}
public class TagColumn extends Column<DataType, String> {
private TagEnum tag;
public TagColumn(TagEnum tag) {
super(new ButtonCell());
this.tag = tag;
setFieldUpdater(new FieldUpdater<DataType, String>() {
#Override
public void update(int index, DataType object, String value) {
Window.alert("Tag " + getTag().getName() + " clicked");
}
});
}
public TagEnum getTag() {
return tag;
}
#Override
public String getValue(DataType object) {
return tag.getName();
}
}
public class DataType {
List<TagEnum> tagList;
public DataType(List<TagEnum> tagList) {
this.tagList = tagList;
}
public List<TagEnum> getTagList() {
return tagList;
}
}
public enum TagEnum {
gwt ("gwt"),
table ("table"),
datagrid ("datagrid"),
widget ("widget"),
customCell ("custom-cell");
private String name;
private TagEnum(String name) {
this.name = name;
}
public String getName() {
return name;
}
}

UWP Custom ListView to scroll down

So, I have a listview and I want it whenever an item is created to scroll to that item (bottom). Because I am using MVVM I found really nice explanation on how to make a new control that inherits from listview that scrolls down. The problem is that this answer (the third) is referring to WPF 6 years ago.
I am making a UWP app, so I copied the code and tried to format it to my needs. The following code doesn't give any error or exception but instead it loads the "ChatListView" as I call it perfectly and then does nothing. The comments are only a bit edited compared to the original code.
What can I do ? Thank you in advance!
public class ChatListView : ListView
{
//Define the AutoScroll property. If enabled, causes the ListBox to scroll to
//the last item whenever a new item is added.
public static readonly DependencyProperty AutoScrollProperty =
DependencyProperty.Register(
"AutoScroll",
typeof(Boolean),
typeof(ChatListView),
new PropertyMetadata(
true, //Default value.
new PropertyChangedCallback(AutoScroll_PropertyChanged)));
//Gets or sets whether or not the list should scroll to the last item
//when a new item is added.
public bool AutoScroll
{
get { return (bool)GetValue(AutoScrollProperty); }
set { SetValue(AutoScrollProperty, value); }
}
//Event handler for when the AutoScroll property is changed.
//This delegates the call to SubscribeToAutoScroll_ItemsCollectionChanged().
//d = The DependencyObject whose property was changed.</param>
//e = Change event args.</param>
private static void AutoScroll_PropertyChanged(
DependencyObject d, DependencyPropertyChangedEventArgs e)
{
SubscribeToAutoScroll_ItemsCollectionChanged(
(ChatListView)d,
(bool)e.NewValue);
}
//Subscribes to the list items' collection changed event if AutoScroll is enabled.
//Otherwise, it unsubscribes from that event.
//For this to work, the underlying list must implement INotifyCollectionChanged.
//
//(This function was only creative for brevity)
//listBox = The list box containing the items collection.
//subscribe = Subscribe to the collection changed event?
private static void SubscribeToAutoScroll_ItemsCollectionChanged(
ChatListView listView, bool subscribe)
{
INotifyCollectionChanged notifyCollection =
listView as INotifyCollectionChanged;
if (notifyCollection != null)
{
if (subscribe)
{
//AutoScroll is turned on, subscribe to collection changed events.
notifyCollection.CollectionChanged +=
listView.AutoScroll_ItemsCollectionChanged;
}
else
{
//AutoScroll is turned off, unsubscribe from collection changed events.
notifyCollection.CollectionChanged -=
listView.AutoScroll_ItemsCollectionChanged;
}
}
}
//Event handler called only when the ItemCollection changes
//and if AutoScroll is enabled.
//sender = The ItemCollection.
//e = Change event args.
private void AutoScroll_ItemsCollectionChanged(
object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
int count = Items.Count;
ScrollIntoView(Items[count - 1]);
}
}
//Constructor a new ChatListView.
public ChatListView()
{
//Subscribe to the AutoScroll property's items collection
//changed handler by default if AutoScroll is enabled by default.
SubscribeToAutoScroll_ItemsCollectionChanged(
this, (bool)AutoScrollProperty.GetMetadata(typeof(ChatListView)).DefaultValue);
}
}
If you want to create a chat application you can use the ItemsStackPanel's ItemsUpdatingScrollMode particular property to KeepLastItemInView value to scroll to the latest item.
Usage:
<ListView>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsStackPanel ItemsUpdatingScrollMode="KeepLastItemInView" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
Note: KeepLastItemInView enum member was introduced in the 14393 SDK.
Related link:
https://learn.microsoft.com/en-us/uwp/api/Windows.UI.Xaml.Controls.ItemsStackPanel#properties_
The accepted answer is pretty nice. However I there is one thing it won't do (at least if I simply copy and paste the above XAML): it won't do its intended scrolling if, say, the user was away from that page while new items were added, and then they navigated to the page.
For that I had to hook into
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
if (MyListView.Items.Count == 0)
return;
object lastItem = MyListView.Items[MyListView.Items.Count - 1];
MyListView.ScrollIntoView(lastItem);
}

Change value of widget inside GWT flex table when other widget's value changes?

Ok, so I have a pretty specific and to me quite complicated issue, as I'm a GWT newbie.
I have a GWT flex table, which I use to dynamically add rows, whose cells contain GWT widgets. The row number changes, but the number of columns in static, always 6. Each row contains a cell with a remove button and five cells each with their own textbox.
What I need to do is somehow code a kind of relationship between the textbox in cell 6 of one row and the textbox in cell 5 in the next row (and vice versa).
To illustrate: when something changes in the textbox at [1,6] the content of textbox at [2,5] needs to be overwritten with the same value. If the textbox at [2,5] changes the textbox at [1,6] needs to change as well. I cannot use a button to commit the changes, it needs to happen via onValueChange or Blur or something similar, which doesn't require the user to perform a specific action.
My problem stems mostly from trying to figure out how to address specific cells in the flex table and their content. For the remove button the solution was easy enough with a click event handler, but for this issue I just can't seem to be able to come up with a solution.
Sadly I also cannot provide any of the code which I have up until now, since it's a business secret. I can only give a broad description of the problem like the one above.
EDIT:
Actually, it's probably more a problem of not having much code in terms of this specific problem.
What I have is a flex table, which has initially only the header row. Upon clicking a button below this table the addNewField() method is called, which just contains the creation, setting of default values and adding of the text fields into a new row.
addNewField() {
int rows = flextable.getRowCount();
Button removeBtn = new Button("x");
removeBtn.getElement().setId(Integer.toString(rows));
//then the button's event handler
TextBox name = new TextBox();
name.setText("something");
flextable.setWidget(rows, 0, "name");
//repeat 4 more times with incrementing columns for the other widgets
}
This way I add entire rows of editable TextBoxes. What I need is a way to influence the values of the 6th column TextBox of a chosen row and the 5th column TextBox of chosen row + 1.
EDIT2: I've tried the dirty option just to see how it would go and somehow the compare inside the if breaks the app. The compiler detects a nullpointerexception and I can't even debug it with breakpoints because it fails to compile and won't start. I can't figure out why though. I threw the code directly into the event for testing purposes, so pardon the ugliness.
TextBox bis = new TextBox();
bis.setText(rows + ":10:00");
subs.setWidget(rows, 5, bis);
bis.addValueChangeHandler(new ValueChangeHandler<String>()
{
#Override
public void onValueChange(ValueChangeEvent<String> event)
{
allRows: for (int i = 0; i < subs.getRowCount(); i++)
{
for (int j = 0; j < subs.getCellCount(i); j++)
{
if ( subs.getWidget(i, j) == bis )
{
TextBox widgetAtColumnSix = ((TextBox) subs.getWidget(i, 5));
String text = widgetAtColumnSix.getText();
TextBox widgetAtColumnFiveRowPlusOne = ((TextBox) subs.getWidget(i + 1, 4));
widgetAtColumnFiveRowPlusOne.setText(text);
break allRows;
}
}
}
}
});
EDIT: Since you edited your question and you dont want to use EventBus you could iterate over your FlexTable and set your TextBox value depending on your current rowIndex and cellIndex... Its not nice but it should work:
public class CellWidget extends Composite {
private TextBox nameBox;
public CellWidget() {
FlowPanel flowPanel = new FlowPanel();
Button deleteButton = new Button("x");
nameBox = new TextBox();
nameBox.addValueChangeHandler(new ValueChangeHandler<String>() {
#Override
public void onValueChange(ValueChangeEvent<String> event) {
notifiyTextBox(CellWidget.this, event.getValue());
}
});
flowPanel.add(nameBox);
flowPanel.add(deleteButton);
initWidget(flowPanel);
}
public void setText(String text) {
nameBox.setText(text);
}
}
public void notifiyTextBox(CellWidget source, String string) {
rows: for (int i = 0; i < flextable.getRowCount(); i++) {
columns: for (int j = 0; j < flextable.getCellCount(i); j++) {
if (flextable.getWidget(i, j) == source) {
CellWidget widgetAtColumnSix = ((CellWidget) flextable.getWidget(i, 5));
widgetAtColumnSix.setText(string);
CellWidget widgetAtColumnFiveRowPlusOne = ((CellWidget) flextable.getWidget(i + 1, 4));
widgetAtColumnFiveRowPlusOne.setText(string);
break rows;
}
}
}
}
I still would recommend using an eventbus. To make it even more convenient there is the GWT Event Binder lib, which makes using events a breeze.
So when you change a value in your textbox[2,5] it also fires your CustomEvent. All Widgets, that need to change their textbox value just need to catch...

How can I click on a View in ListView specific row position

I have a ListView:
And I want to click on a specific button within a ListView.
If I want to select with the onData selector:
onData(withId(R.id.button))
.inAdapterView(withId(R.id.list_view))
.atPosition(1)
.perform(click());
And I get this error:
android.support.test.espresso.PerformException: Error performing 'load adapter data' on view 'with id: com.example.application:id/list_view'.
...
How can I solve this?
onData() requires an object matcher for the item that you are interested in. If you don't care about the data in the adapter you can use Matchers.anything() to effectively match all objects in the adapter. Alternatively you can create a data matcher (depending on data that is stored in the adapter) for your item and pass it in for a more deterministic test.
As for the button - what you are looking for is an onChildsView() method, which allows to pass a viewmatcher for the descendant of the listitem, that was matched in the onData().atPosition()
And as a result your test will look something like this:
onData(anything()).inAdapterView(withId(R.id.list_view))
.atPosition(1)
.onChildView(withId(R.id.button))
.perform(click());
I used a workaround which don't use the ListView data, and the .getPosition(index), instead checks that the the view with the specific id is the descendant of the ListView specific position View.
public static Matcher<View> nthChildsDescendant(final Matcher<View> parentMatcher, final int childPosition) {
return new TypeSafeMatcher<View>() {
#Override
public void describeTo(Description description) {
description.appendText("with " + childPosition + " child view of type parentMatcher");
}
#Override
public boolean matchesSafely(View view) {
while(view.getParent() != null) {
if(parentMatcher.matches(view.getParent())) {
return view.equals(((ViewGroup) view.getParent()).getChildAt(childPosition));
}
view = (View) view.getParent();
}
return false;
}
};
}
Example of usage:
onView(allOf(
withId(R.id.button),
nthChildsDescendant(withId(R.id.list_view), 1)))
.perform(click());

Problems with MvxSpinner in ListView

I'm having a problem where I have a listview that contains a group of spinners. If I select an option for the first spinner and then scroll down I'll see a spinner that I haven't even touched has the same value as the first spinner I just set. I'm assuming this is an issue with the Spinner view being recycled and improperly used below. Has anyone else ran into this issue with spinners? I'm thinking we need to implement a solution similar to this in MvxAdapter?
I implemented my own MyMvxAdapter and MyMvxListView to handle this. The only thing I changed in the MyMvxListView was to have it use MyMvxAdapter as its adapter instead of the normal MvxAdapter. I then changed the GetBindableView in MyMvxAdapter to look like this:
protected virtual View GetBindableView(View convertView, object dataContext, int templateId)
{
if (templateId == 0)
{
// no template seen - so use a standard string view from Android and use ToString()
return GetSimpleView(convertView, dataContext);
}
// we have a templateid so lets use bind and inflate on it :)
var viewToUse = convertView as IMvxListItemView;
if (viewToUse != null)
{
if (viewToUse.TemplateId != templateId)
{
viewToUse = null;
}
}
if (viewToUse == null)
{
viewToUse = CreateBindableView(dataContext, templateId);
}
else
{
var spinner = (MvxSpinner)convertView.FindViewById(Resource.Id.taskFieldSpinner);
if (spinner != null)
{
spinner.SetSelection(((WrappedEmployeeTaskField)dataContext).TheField.SpinnerSelection);
}
BindBindableView(dataContext, viewToUse);
}
return viewToUse as View;
}
You'll notice the only real difference is that I needed to directly access my spinner resource to properly set it if viewToUse is not null. Then the last of the "magic sauce" was to keep track of the spinner's selected value on my data model, in this case as the property "SpinnerSelection" on my model which gets filled in every time the value gets selected.