Get ListCell via ListView - javafx

Question

I have a ListView with my own ListCell<MyObject> implementation. Via a network signal, I receive an index of my ListCell that should be changed.
Over listView.getItems().get(index); there is no problem to access the model, but I want to make a layout change to the listCell with the received index and a layout change to the ListCell with the index+1;
How can I access the ListCell via the ListView?
I search for a method like this:
listView.getListCell(index);

Answer 1

Unfortunately right now there is no API to get List Cell by index or to get All children's(listcells) for ListView. One solution can be, define a new StringProperty specialIndicator in your MyObject class.
class MyObject {
....//u r properties
private StringProperty specialIndicator;
When ever you get index from network signal set this specialIndicator property of object and do forcerefresh of ListView
public void onReceivedNetWorkSignalIndex() {
listView.getItems().get(indexFromService).setSpecialIndicator("selected");
listView.getItems().get(indexFromService+1).setSpecialIndicator("selectedplusone");
//force refresh listview (it will trigger cellFactory again so that you can manipulate layout)
listView.setItems(null);
listView.setItems(allObjects);
}
As you already have custom Object ListView , i am assuming you already have custom cellFactory (if not you have to create one ) ,Modify your custom cell factory to handle this special Indicators
listView.setCellFactory(new Callback<ListView<MyObject>, ListCell<MyObject>>() {
#Override
public ListCell<MyObject> call(ListView<MyObject> myObjectListView) {
ListCell<MyObject> cell = new ListCell<MyObject>(){
#Override
protected void updateItem(MyObject myObject, boolean b) {
super.updateItem(myObject, b);
if(myObject != null) {
setText(myObject.getName());
if("selected".equalsIgnoreCase(myObject.getSpecialIndicator())) {
System.out.println("Setting new CSS/graphics for index retun from service." + myObject.getName());
} else if("selectedplusone".equalsIgnoreCase(myObject.getSpecialIndicator())) {
System.out.println("Setting new CSS/Graphics for index+1 returned from service" + myObject.getName());
}
myObject.setSpecialIndicator(""); // reset it back to empty
}
}
};
return cell;
}
});
Here is the whole sample Application ,you can look into it (in case the above explanation is not clear).
public class ListViewTest extends Application {
#Override
public void start(Stage stage) throws Exception {
VBox root = new VBox();
final ObservableList<MyObject> allObjects = FXCollections.observableArrayList(new MyObject("object0"), new MyObject("object1"),new MyObject("object2"),new MyObject("object3"),new MyObject("object4"));
final ListView<MyObject> listView = new ListView<>(allObjects);
listView.setCellFactory(new Callback<ListView<MyObject>, ListCell<MyObject>>() {
#Override
public ListCell<MyObject> call(ListView<MyObject> myObjectListView) {
ListCell<MyObject> cell = new ListCell<MyObject>(){
#Override
protected void updateItem(MyObject myObject, boolean b) {
super.updateItem(myObject, b);
if(myObject != null) {
setText(myObject.getName());
if("selected".equalsIgnoreCase(myObject.getSpecialIndicator())) {
System.out.println("Setting new CSS/graphics for index retun from service." + myObject.getName());
setText("I am selected Index from Service");
} else if("selectedplusone".equalsIgnoreCase(myObject.getSpecialIndicator())) {
System.out.println("Setting new CSS/Graphics for index+1 returned from service" + myObject.getName());
setText("I am selected Index +1 from Service");
}
myObject.setSpecialIndicator(""); // reset it back to empty
}
}
};
return cell;
}
});
Button serviceIndex2 = new Button("ServiceIndex2");
serviceIndex2.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent actionEvent) {
int indexFromService =2;
listView.getItems().get(indexFromService).setSpecialIndicator("selected");
listView.getItems().get(indexFromService+1).setSpecialIndicator("selectedplusone");
listView.setItems(null);
listView.setItems(allObjects);
}
});
root.getChildren().addAll(listView,serviceIndex2);
Scene scene = new Scene(root,500,500);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
class MyObject {
private StringProperty name;
private StringProperty specialIndicator;
MyObject(String name) {
this.name = new SimpleStringProperty(name);
this.specialIndicator = new SimpleStringProperty();
}
public String getName() {
return name.get();
}
public StringProperty nameProperty() {
return name;
}
public void setName(String name) {
this.name.set(name);
}
public String getSpecialIndicator() {
return specialIndicator.get();
}
public StringProperty specialIndicatorProperty() {
return specialIndicator;
}
public void setSpecialIndicator(String specialIndicator) {
this.specialIndicator.set(specialIndicator);
}
}
}

Answer 2

Here's a relatively simple approach, where there is just one "selected" index. Here I create a property to hold the index that is selected, and the cell factory just observes it, along with the cell's item property and index property, and sets the text via a binding. You could do something similar to set the graphic, if needed.
import java.util.concurrent.Callable;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.util.Callback;
public class ListViewStyleAroundSelection extends Application {
#Override
public void start(Stage primaryStage) {
final ListView<String> listView = new ListView<>();
for (int i=1; i<=20; i++) {
listView.getItems().add("Item "+i);
}
final HBox controls = new HBox(5);
final Button button = new Button("Set selection");
final TextField indexField = new TextField();
final IntegerProperty selectionIndex = new SimpleIntegerProperty();
button.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
try {
selectionIndex.set(Integer.parseInt(indexField.getText()));
} catch (NumberFormatException nfe) {
indexField.setText("");
}
}
});
controls.getChildren().addAll(new Label("Enter selection index:"), indexField, button);
final BorderPane root = new BorderPane();
root.setCenter(listView);
root.setBottom(controls);
listView.setCellFactory(new Callback<ListView<String>, ListCell<String>>() {
#Override
public ListCell<String> call(ListView<String> lv) {
final ListCell<String> cell = new ListCell<>();
cell.textProperty().bind(Bindings.createStringBinding(new Callable<String>() {
#Override
public String call() throws Exception {
if (cell.getItem() == null) {
return null ;
} else {
switch (cell.getIndex() - selectionIndex.get()) {
case -1: return cell.getItem() + " (selected item below)";
case 0: return cell.getItem() + " (selected)";
case 1: return cell.getItem() + " (selected item above)";
default: return cell.getItem();
}
}
}
}, cell.itemProperty(), cell.indexProperty(), selectionIndex));
return cell;
}
});
final Scene scene = new Scene(root, 600, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
And here's a slightly more complex version. Here I have a custom data type which includes a boolean property. The update sets the boolean property of the specified item to true. The cell factory creates a cell, and observes the selected property both of the current item and of the previous item. Then, as before, it uses a binding to update the text of the cell.
import java.util.concurrent.Callable;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.beans.binding.IntegerBinding;
import javafx.beans.binding.ObjectBinding;
import javafx.beans.binding.StringBinding;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.util.Callback;
public class ListViewStyleAroundSelection extends Application {
#Override
public void start(Stage primaryStage) {
final ListView<MyDataType> listView = new ListView<>();
for (int i=0; i<=20; i++) {
listView.getItems().add(new MyDataType("Item "+i, false));
}
final HBox controls = new HBox(5);
controls.setPadding(new Insets(5));
final Button button = new Button("Set selection");
final TextField indexField = new TextField();
button.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
try {
int index = Integer.parseInt(indexField.getText());
if (index >= 0 && index < listView.getItems().size()) {
final MyDataType item = listView.getItems().get(index);
item.setSelected( ! item.isSelected() );
}
} catch (NumberFormatException nfe) {
indexField.setText("");
}
}
});
controls.getChildren().addAll(new Label("Enter selection index:"), indexField, button);
final BorderPane root = new BorderPane();
root.setCenter(listView);
root.setBottom(controls);
listView.setCellFactory(new Callback<ListView<MyDataType>, ListCell<MyDataType>>() {
#Override
public ListCell<MyDataType> call(ListView<MyDataType> lv) {
final ListCell<MyDataType> cell = new ListCell<>();
final IntegerBinding previousIndex = cell.indexProperty().subtract(1);
final ObjectBinding<MyDataType> previousItem = Bindings.valueAt(listView.getItems(), previousIndex);
final BooleanBinding previousItemSelected = Bindings.selectBoolean(previousItem, "selected");
final StringBinding thisItemName = Bindings.selectString(cell.itemProperty(), "name");
final BooleanBinding thisItemSelected = Bindings.selectBoolean(cell.itemProperty(), "selected");
cell.textProperty().bind(Bindings.createStringBinding(new Callable<String>() {
#Override
public String call() throws Exception {
if (cell.getItem() == null) {
return null ;
} else {
String value = cell.getItem().getName();
if (thisItemSelected.get()) {
value = value + " (selected) " ;
} else if (previousItemSelected.get()) {
value = value + " (selected item is above)";
}
return value ;
}
}
}, thisItemName, thisItemSelected, previousItemSelected));
return cell;
}
});
final Scene scene = new Scene(root, 600, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static class MyDataType {
private final BooleanProperty selected ;
private final StringProperty name ;
public MyDataType(String name, boolean selected) {
this.name = new SimpleStringProperty(this, "name", name);
this.selected = new SimpleBooleanProperty(this, "selected", selected);
}
public final String getName() {
return name.get();
}
public final void setName(String name) {
this.name.set(name);
}
public final StringProperty nameProperty() {
return name ;
}
public final boolean isSelected() {
return selected.get();
}
public final void setSelected(boolean selected) {
this.selected.set(selected);
}
public final BooleanProperty selectedProperty() {
return selected;
}
}
public static void main(String[] args) {
launch(args);
}
}

Answer 3

Cell has a style class called ".cell"
public Cell getListCell(ListView list, int index){
Object[]cells = list.lookupAll(".cell").toArray();
return (Cell)cells[index];
}

Answer 4

This is the method I used to solve the same problem. Please note that getting the cell view is considered bad practice, and shouldn't be done in a normal context, updating cells should only be done through the model, my special case was that I wanted to fire an event manually as part of a workaround.
private ListCell<?> getListCell(ListView<?> listView, int cellIndex) {
if (cellIndex == -1) {
return null;
}
//Virtual Flow is the container of all list cells
//Each ListView has exactly one VirtualFlow which we are searching for
Optional<VirtualFlow> virtualFlowOptional = listView.getChildrenUnmodifiable()
.stream()
.filter(node -> node instanceof VirtualFlow)
.map(n -> (VirtualFlow) n)
.findFirst();
if (virtualFlowOptional.isEmpty()) {
return null;
}
VirtualFlow<ListCell<?>> virtualFlow = virtualFlowOptional.get();
return virtualFlow.getCell(cellIndex);
}