JavaFX_TableView_如果使用哈希图，如何为特定单元格填充颜色

Question

I have created a Java TableView using a hashmap for the data. Within the hashmap, the key is a certain word, and the value is how often this word is included. I also implemented an ObservableList for the dataModel.

Let´s say, we have a tableview in which the first column represents capital cities (key of hashmap) and the second column represents how often a certain city has been visited (value of hashmap), ie

Cities          No. of times visited

Amsterdam                2

Berlin                   4

Rome                     6

I now want to fill certain cells in the 2nd column with a color. For example, all cells with a value of greater than 2 should be yellow, values >4 should be orange and values >6 should be red. But I don´t know how to do that. Here are some code snippets which show what I alreday did:

//create HashMap
HashMap<String, Integer[]> listMap;

//ObservableList
public static ObservableList<Map.Entry<String, Integer[]>> items;

//create table
TableView<Map.Entry<String, Integer[]>> table = new TableView<>(items);

//column words (key of hashmap)
words.setCellValueFactory(new PropertyValueFactory<>("words"));

//return property from hashmap for cell 
words.setCellValueFactory(new Callback<TableColumn.CellDataFeatures<Map.Entry<String, Integer[]>, String>, ObservableValue<String>>()
{
    @Override
    public ObservableValue<String> call(TableColumn.CellDataFeatures<Map.Entry<String, Integer[]>, String> p)
    {                     
        return new SimpleStringProperty(p.getValue().getKey()); 
    }       
});

firstColumn.setCellValueFactory(new Callback<TableColumn.CellDataFeatures<Map.Entry<String, Integer[]>, String>, ObservableValue<String>>()
{
    @Override
    public ObservableValue<String> call(TableColumn.CellDataFeatures<Map.Entry<String, Integer[]>, String> p)
            {
                return new SimpleStringProperty(String.valueOf(p.getValue().getValue());
            }         
});   

Does anyone have a solution to this issue? Thanks :)

Answer 1

Use the cell factory to define the rendering behavior of the cell. The cell value factory only defines the populating behavior.

Example:

firstColumn.setCellFactory(column -> {
        return new TableCell<YourObject, Integer>() {

            @Override
            protected void updateItem(Integer item, boolean empty) {
                super.updateItem(item, empty);

                if (item == null || empty) {
                    setBackground(new Background(new BackgroundFill(Color.WHITE, CornerRadii.EMPTY, Insets.EMPTY)));
                } else {

                    if(item > 2)
                        setBackground(new Background(new BackgroundFill(Color.YELLOW, CornerRadii.EMPTY, Insets.EMPTY)));
                    else if(item > 4)
                        setBackground(new Background(new BackgroundFill(Color.RED, CornerRadii.EMPTY, Insets.EMPTY)));
                    else
                        setBackground(new Background(new BackgroundFill(Color.WHITE, CornerRadii.EMPTY, Insets.EMPTY)));
                }
            }
        };
});

If you want to display a text associated with the value, let's say "OK" when value < 2, "Warning" when value > 2 and "Danger" when value > 4, you can do it with setText("Some text") just next to the setBackground() . The cell will then display the text depending on the value of the cell.

if (item == null || empty) {
    setText("");
    setBackground(new Background(new BackgroundFill(Color.WHITE, CornerRadii.EMPTY, Insets.EMPTY)));
} else {

    if(item > 2) {
        setText("Warning");
        setBackground(new Background(new BackgroundFill(Color.YELLOW, CornerRadii.EMPTY, Insets.EMPTY)));
    } else if(item > 4) {
        setText("Danger");
        setBackground(new Background(new BackgroundFill(Color.RED, CornerRadii.EMPTY, Insets.EMPTY)));
    } else {
        setText("OK");
        setBackground(new Background(new BackgroundFill(Color.WHITE, CornerRadii.EMPTY, Insets.EMPTY)));
    }
}