我正在尝试从使用 Java 保存在 sql 数据库中的数据生成统计图(BarCharts 和 LineCharts)。数据预计会不时发生变化。
我曾尝试使用 ObservableLists,但收到错误消息。
以下是我迄今为止尝试过的;注意:这驻留在 DatabaseHandler 类中
public ObservableList<BarChart.Data> getItemGraphStatistics(){
ObservableList<BarChart.Data> data = FXCollections.observableArrayList();
String sql = "SELECT itemID, COUNT(*) FROM (SELECT itemID FROM SALES UNION ALL SELECT itemID FROM STOCK) t GROUP BY itemID";
System.out.println(sql );
ResultSet rs = handler.execQuery(sql);
try{
while(rs.next()){
String item= rs.getString("itemID");
int count = rs.getInt(2);
data.add(new BarChart.Data(item+ "(" + count + ")", count));
}
} catch (SQLException ex) {
Logger.getLogger(DatabaseHandler.class.getName()).log(Level.SEVERE, null, ex);
}
return data;
}
在运行上面我得到
java.lang.ClassCastException: javafx.scene.chart.XYChart$Data cannot be cast to javafx.scene.chart.XYChart$Series
当我尝试将 BarChart.Data 更改为 BarChart.Series 时,我无法将 int 转换为 observableList 错误消息。
以下是上述试验的示例;
import com.jfoenix.controls.JFXButton;
import com.jfoenix.controls.JFXRadioButton;
import com.jfoenix.controls.JFXTextField;
import java.net.URL;
import java.util.Calendar;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.ResourceBundle;
import java.util.concurrent.TimeUnit;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.chart.BarChart;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.PieChart;
import javafx.scene.control.ChoiceBox;
import javafx.scene.control.DatePicker;
import javafx.scene.control.ToggleGroup;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.HBox;
import sales.manager.database.DatabaseHandler;
/**
* FXML Controller class
*
* @author Garande
*/
public class PerformanceAnalyzerController implements Initializable {
@FXML
private AnchorPane analysisHandler;
@FXML
private AnchorPane graphHandler;
@FXML
private PieChart piechart;
@FXML
private BarChart<?, ?> barchart;
@FXML
private LineChart<?, ?> linechart;
@FXML
private NumberAxis yBarGraph;
@FXML
private CategoryAxis xBarGraph;
@FXML
private NumberAxis yLineGraph;
@FXML
private CategoryAxis xLineGraph;
DatabaseHandler handler = DatabaseHandler.getInstance();
/**
* Initializes the controller class.
*/
@Override
public void initialize(URL url, ResourceBundle rb) {
}
@FXML
private void performAnalysisOperation(ActionEvent event) {
//Performing analysis operation
barchart.setData(handler.getItemGraphStatistics());
graphHandler.getChildren().add(barchart);
}
}
data
an的属性XYChart
持有一个ObservableList<XYChart.Series>
。每个XYChart.Series
也有一个data
属性,但它持有一个ObservableList<XYChart.Data>
. 问题是您的方法返回一个ObservableList<XYChart.Data>
,然后您尝试设置它XYChart.data
- 类型不匹配。我不确定你是如何得到 a 的ClassCastException
,因为你的代码甚至不应该编译。
您需要将数据列表包装在一个系列中,然后将该系列添加到图表中。您还应该避免使用原始类型。双方Series
并Data
具有类型参数,但你不指定它们。根据您构建 的方式Data
,您的代码应该类似于(为简洁起见省略了一些代码):
public class PerformanceAnalyzerController {
@FXML private BarChart<String, Number> barChart;
@FXML
private void performAnalysisOperation(ActionEvent event) {
//Performing analysis operation
ObservableList<XYChart.Data<String, Number>> data = handler.getItemsGraphicsStatisitics();
XYChart.Series<String, Number> series = new XYChart.Series<>("Series Name", data);
barchart.getData().setAll(series);
graphHandler.getChildren().add(barchart);
}
}
和:
// Use generic types
public ObservableList<XYChart.Data<String, Number>> getItemGraphStatistics(){
ObservableList<XYChart.Data<String, Number>> data = FXCollections.observableArrayList();
String sql = "SELECT itemID, COUNT(*) FROM (SELECT itemID FROM SALES UNION ALL SELECT itemID FROM STOCK) t GROUP BY itemID";
System.out.println(sql );
ResultSet rs = handler.execQuery(sql);
try{
while(rs.next()){
String item= rs.getString("itemID");
int count = rs.getInt(2);
// add diamond operator "<>"
data.add(new XYChart.Data<>(item+ "(" + count + ")", count));
}
} catch (SQLException ex) {
Logger.getLogger(DatabaseHandler.class.getName()).log(Level.SEVERE, null, ex);
}
return data;
}
注意:我替换了BarChart.Data
with 的使用XYChart.Data
,但我认为在这种情况下这无关紧要。
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