I need to show different tool tip for each table cell - javafx-8

Question

Please see this
This is what I want to see... I mean the tool tip
At run time I get this error message for each row that is being loaded.
The tool tip text lies in the an object and is retrieved by thisRow.getCourseTootip(i);
Number of columns in the table varies and I create them and add them to the table view thru code.
for (int courseNo = 0; courseNo < numberOfCourses; courseNo++) {
String colName = getASemesterCourse(thisSemester, courseNo).getCourseID();
TableColumn<AResultRow, String> thisColumn = new TableColumn<>(colName);
thisColumn.setPrefWidth(80);
thisColumn.setStyle("-fx-alignment: CENTER; font-weight:bold;");
String str = TableRows.get(1).getGrade(courseNo);
final int i = courseNo;
thisColumn.setCellValueFactory(cellData -> cellData.getValue().courseGradeProperty(i));
thisColumn.setCellFactory(new Callback<TableColumn<AResultRow, String>, TableCell<AResultRow, String>>() {
public TableCell<AResultRow, String> call(TableColumn<AResultRow, String> column) {
return new TableCell<AResultRow, String>() {
#Override
protected void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
if (!empty) {
setText(item);
AResultRow thisRow = new AResultRow();
thisRow = getTableView().getItems().get(getTableRow().getIndex());
final Tooltip tip= new Tooltip();
tip.setText(thisRow.getCourseTootip(i));
setTooltip(tip);
tip.setStyle("-fx-background-color: pink; -fx-text-fill: black; -fx-font: normal normal 12pt \"Times New Roman\"");
}
}
};
}
});
boolean retVal = thisTable.getColumns().addAll(thisColumn);
}
Error is
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at victoriairene.TheMainFXMLController$1$1.updateItem(TheMainFXMLController.java:434)
at victoriairene.TheMainFXMLController$1$1.updateItem(TheMainFXMLController.java:427)
Line 434 is
thisRow = getTableView().getItems().get(getTableRow().getIndex());
Text for the tool tip for this cell comes from thisRow.getCourseTootip(i).
Can someone tell me, what is wrong with my code? Which object is null ? If it is null, then how do I get to see the correct Tooltip text, in spite of getting error messages for each row ?
I have been struggling with this for one full day.
Please help and thanks in advance.
As requested by Kleopatra I am enclosing the entire Create Table function.
public void createTableForThisSemester(int thisSemester, int numberOfCourses, javafx.collections.ObservableList<AResultRow> TableRows) {
TableView<AResultRow> thisTable = new TableView<>();
thisTable.setContextMenu(contextMenu);
TableColumn<AResultRow, String> tcolRollNo = new TableColumn<>("Roll Number");
tcolRollNo.setEditable(false);
tcolRollNo.setPrefWidth(120);
TableColumn<AResultRow, String> tcolName = new TableColumn<>("Student Name");
tcolName.setEditable(false);
tcolName.setPrefWidth(350);
tcolRollNo.setCellValueFactory(cellData -> cellData.getValue().StudentIDProperty());
tcolName.setCellValueFactory(cellData -> cellData.getValue().StudentNameProperty());
boolean xyz = thisTable.getColumns().addAll(tcolRollNo, tcolName);
// TableColumn[] courseColumn = new TableColumn[numberOfCourses];
for (int courseNo = 0; courseNo < numberOfCourses; courseNo++) {
String colName = getASemesterCourse(thisSemester, courseNo).getCourseID();
TableColumn<AResultRow, String> thisColumn = new TableColumn<>(colName);
thisColumn.setPrefWidth(80);
thisColumn.setStyle("-fx-alignment: CENTER; font-weight:bold;");
String str = TableRows.get(1).getGrade(courseNo);
final int i = courseNo;
thisColumn.setCellValueFactory(cellData -> cellData.getValue().courseGradeProperty(i));
thisColumn.setCellFactory(new Callback<TableColumn<AResultRow, String>, TableCell<AResultRow, String>>() {
public TableCell<AResultRow, String> call(TableColumn<AResultRow, String> column) {
return new TableCell<AResultRow, String>() {
#Override
protected void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
if (!empty) {
setText(item);
AResultRow thisRow = new AResultRow();
thisRow = getTableView().getItems().get(getTableRow().getIndex());
final Tooltip tip= new Tooltip();
tip.setText(thisRow.getCourseTootip(i));
setTooltip(tip);
tip.setStyle("-fx-background-color: pink; -fx-text-fill: black; -fx-font: normal normal 12pt \"Times New Roman\"");
}
}
};
}
});
boolean retVal = thisTable.getColumns().addAll(thisColumn);
}
// System.out.println("# of Rows in Table [" + thisSemester + "] = " + TableRows.size());
TableColumn<AResultRow, String> tcolGPA = new TableColumn<>("GPA");
tcolGPA.setEditable(false);
tcolGPA.setPrefWidth(80);
tcolGPA.setStyle("-fx-alignment: CENTER; font-weight:bold;");
tcolGPA.setCellValueFactory(cellData -> cellData.getValue().returnStringGPA());
boolean retVal = thisTable.getColumns().addAll(tcolGPA);
thisTable.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
thisTable.setItems(TableRows);
thisTable.getSelectionModel().selectedItemProperty().addListener((observableValue, oldValue, newValue) -> {
//Check whether item is selected and set value of selected item to Label
if (thisTable.getSelectionModel().getSelectedItem() == null) {
gRollNumber = null;
gStudentName = null;
} else {
gRollNumber = newValue.getStudentID();
gStudentName = newValue.getStudentName();
}
});
ScrollPane thisScrollPane = new ScrollPane();
thisScrollPane.setFitToWidth(true);
thisScrollPane.setFitToHeight(true);
thisScrollPane.setMinHeight((theDetails.getHeight() - 25));
thisScrollPane.setMaxHeight((theDetails.getHeight() - 25));
thisScrollPane.setMinWidth((theDetails.getWidth() - 25));
thisScrollPane.setHbarPolicy(ScrollPane.ScrollBarPolicy.ALWAYS);
Tab thisTab = tabs.getTabs().get(thisSemester);
thisTab.setContent(thisScrollPane);
thisScrollPane.setContent(thisTable);
}
I am repeating the hierarchy again - please excuse.
Table view is associated with an observablelist named ATableRows which a class ATableRow.
ATableRow contains several members and one of them is an array of class ACourseResult.
I need to know the ROW number and the array index (which is actually the Table Column number for that Cell) before I can retrieve the text for the tooltip.
Thing is the code works... except for the runtime error of null pointer. I still do not understand what the CellFactory and CellValueFactories do. Sorry about that. Oracle's documents do not say what they do......
While I am at this.... I want to tell you that my TABLE is READ ONLY. Do I Have to use the Observable List ? Can't I do this by setting values directly to each cell (just a curiosity).
Thanks in advance and sorry if my questions seem dumber.
Thanks to JAMES my problem is solved.... I am enclosing the modified code for others.
for (int courseNo = 0; courseNo < numberOfCourses; courseNo++) {
String colName = getASemesterCourse(thisSemester, courseNo).getCourseID();
TableColumn<AResultRow, String> thisColumn = new TableColumn<>(colName);
thisColumn.setPrefWidth(80);
thisColumn.setStyle("-fx-alignment: CENTER; font-weight:bold;");
String str = TableRows.get(1).getGrade(courseNo);
final int i = courseNo;
thisColumn.setCellValueFactory(cellData -> cellData.getValue().courseGradeProperty(i));
thisColumn.setCellFactory(new Callback<TableColumn<AResultRow, String>, TableCell<AResultRow, String>>() {
public TableCell<AResultRow, String> call(TableColumn<AResultRow, String> column) {
return new TableCell<AResultRow, String>() {
#Override
protected void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
if (!empty) {
setText(item);
AResultRow thisRow = new AResultRow();
final int k = this.getIndex(); **// These are the changes suggested by James**
thisRow = getTableView().getItems().get(k); ***// These are the changes suggested by James***
// thisRow = getTableView().getItems().get(getTableRow().getIndex()); <- this is the old code commented out.
final Tooltip tip= new Tooltip();
tip.setText(thisRow.getCourseTootip(i));
setTooltip(tip);
tip.setStyle("-fx-background-color: pink; -fx-text-fill: black; -fx-font: normal normal 12pt \"Times New Roman\"");
}
}
};
}
});
boolean retVal = thisTable.getColumns().addAll(thisColumn);
}

Answer 1

The quick, and wrong, answer to the question is to point out that TableCell has a getTableRow() method, that will give you the row data without having to look it up through the underlying data via the row index.
Technically, you should give the TableCell all of the information it needs to work independently when its updateItem() method is called. This would mean restructing the data model such that the table cell is given a structure with both the displayed contents of the cell, and the text to go in the tooltip. It would appear that the AResultRow data structure has two associated lists, one with whatever shows in the cell, and the other with whatever goes into the tooltip. My suggestion would be to refactor that so that it's a single list holding objects which contain both data elements. Once you do that, the rest of the table structure becomes trivial. Here's a working example:
public class SampleTable extends Application {
private BorderPane testPane;
class TestPane extends BorderPane {
public TestPane(List<DataModel> dataItems) {
TableView<DataModel> tableView = new TableView<DataModel>();
setCenter(tableView);
TableColumn<DataModel, ClassInfo> column1 = new TableColumn<DataModel, ClassInfo>("column 1");
TableColumn<DataModel, ClassInfo> column2 = new TableColumn<DataModel, ClassInfo>("column 2");
column1.setCellValueFactory(new PropertyValueFactory<DataModel, ClassInfo>("column1Data"));
column2.setCellValueFactory(new PropertyValueFactory<DataModel, ClassInfo>("column2Data"));
column1.setCellFactory(column -> new CustomTableCell());
column2.setCellFactory(column -> new CustomTableCell());
tableView.getColumns().addAll(column1, column2);
tableView.setItems(FXCollections.observableList(dataItems));
}
}
public static void main(String[] args) {
launch(args);
}
public class CustomTableCell extends TableCell<DataModel, ClassInfo> {
#Override
protected void updateItem(ClassInfo item, boolean empty) {
super.updateItem(item, empty);
if (!empty) {
if (item != null) {
setText(item.getName());
setTooltip(new Tooltip(item.getDescription()));
}
}
}
}
#Override
public void start(Stage primaryStage) {
primaryStage.setTitle("Task Progress Tester");
List<DataModel> dataItems = new ArrayList<DataModel>();
DataModel row1Data = new DataModel();
row1Data.setColumn1Data(new ClassInfo("row1Col1Name", "This is the description for Row1, Column 1"));
row1Data.setColumn2Data(new ClassInfo("row1Col2Name", "This is the description for Row1, Column 2"));
dataItems.add(row1Data);
DataModel row2Data = new DataModel();
row2Data.setColumn1Data(new ClassInfo("row2Col1Name", "This is the description for Row2, Column 1"));
row2Data.setColumn2Data(new ClassInfo("row2Col2Name", "This is the description for Row2, Column 2"));
dataItems.add(row2Data);
testPane = new TestPane(dataItems);
primaryStage.setScene(new Scene(testPane, 300, 250));
primaryStage.show();
}
public class DataModel {
private ObjectProperty<ClassInfo> column1Data = new SimpleObjectProperty<ClassInfo>();
private ObjectProperty<ClassInfo> column2Data = new SimpleObjectProperty<ClassInfo>();
public void setColumn2Data(ClassInfo newValue) {
column2Data.set(newValue);
}
public void setColumn1Data(ClassInfo newValue) {
column1Data.set(newValue);
}
public ObjectProperty<ClassInfo> column1DataProperty() {
return column1Data;
}
}
public class ClassInfo {
private String name;
private String description;
public ClassInfo(String name, String description) {
this.setName(name);
this.setDescription(description);
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
}