所以这对我来说非常困惑。我决定将应用程序控制台重定向到 UI 中的 TextArea。
当我在 SceneBuilder 中使用固定文本区域(固定 ID)执行此操作，然后进行注释时
@FXML
private TextArea consoleTextArea;
什么也没发生。内容没有改变。是的，我确实在构造函数中初始化了它。并进一步初始化。 这不是工作代码:
public class ConsoleController implements Initializable {
Thread t;
@FXML
private Label totalM;
@FXML
private Label freeM;
@FXML
private Label maxM;
@FXML
private TextArea consoleTextArea;
private Console console;
private PrintStream ps;
public ConsoleController() {
System.out.println("Called constructor");
totalM = new Label();
freeM = new Label();
maxM = new Label();
consoleTextArea = new TextArea();
console = new Console(consoleTextArea);
ps = new PrintStream(console, true);
}
@Override
public void initialize(URL location, ResourceBundle resources) {
redirectOutput(ps);
t = new Thread(() -> {
while (true) {
try {
Platform.runLater(() -> {
updateMemInfo();
});
Thread.sleep(1000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
});
t.setPriority(Thread.MIN_PRIORITY);
t.setName("MemUpdateInfoThread");
t.setDaemon(true);
t.start();
}
private void updateMemInfo() {
totalM.setText("Total Memory (in bytes): " + Runtime.getRuntime().totalMemory());
freeM.setText("Free Memory (in bytes): " + Runtime.getRuntime().freeMemory());
maxM.setText("Max Memory (in bytes): " + Runtime.getRuntime().maxMemory());
}
private void redirectOutput(PrintStream prs) {
System.setOut(prs);
System.setErr(prs);
}
private void updateConsole(String text) {
for (int c : text.toCharArray()) {
try {
console.write(c);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
private class Console extends OutputStream {
private TextArea txtArea;
public Console(TextArea txtArea) {
this.txtArea = txtArea;
}
@Override
public void write(int b) throws IOException {
txtArea.appendText(String.valueOf((char) b));
}
}
}
经过一番编辑后，我决定不使用fxml id。只将id放在AnchorPane父级上，并在java代码中添加textArea。
@FXML
private AnchorPane anchp;
private TextArea consoleTextArea;
//then added to anchor
anchp.getChildren().add(consoleTextArea);
工作代码:
public class ConsoleController implements Initializable {
Thread t;
@FXML
private Label totalM;
@FXML
private Label freeM;
@FXML
private Label maxM;
@FXML
private AnchorPane anchp;
private TextArea consoleTextArea;
private Console console;
private PrintStream ps;
public ConsoleController() {
System.out.println("Called constructor");
totalM = new Label();
freeM = new Label();
maxM = new Label();
anchp=new AnchorPane();
consoleTextArea = new TextArea();
console = new Console(consoleTextArea);
ps = new PrintStream(console, true);
}
@Override
public void initialize(URL location, ResourceBundle resources) {
anchp.getChildren().add(consoleTextArea);
AnchorPane.setTopAnchor(consoleTextArea, 0d);
AnchorPane.setLeftAnchor(consoleTextArea, 0d);
AnchorPane.setRightAnchor(consoleTextArea, 0d);
AnchorPane.setBottomAnchor(consoleTextArea, 0d);
redirectOutput(ps);
t = new Thread(() -> {
while (true) {
try {
Platform.runLater(() -> {
updateMemInfo();
});
Thread.sleep(1000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
});
t.setPriority(Thread.MIN_PRIORITY);
t.setName("MemUpdateInfoThread");
t.setDaemon(true);
t.start();
}
private void updateMemInfo() {
totalM.setText("Total Memory (in bytes): " + Runtime.getRuntime().totalMemory());
freeM.setText("Free Memory (in bytes): " + Runtime.getRuntime().freeMemory());
maxM.setText("Max Memory (in bytes): " + Runtime.getRuntime().maxMemory());
}
private void redirectOutput(PrintStream prs) {
System.setOut(prs);
System.setErr(prs);
}
private void updateConsole(String text) {
for (int c : text.toCharArray()) {
try {
console.write(c);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
private class Console extends OutputStream {
private TextArea txtArea;
public Console(TextArea txtArea) {
this.txtArea = txtArea;
}
@Override
public void write(int b) throws IOException {
txtArea.appendText(String.valueOf((char) b));
}
}
}
为什么我无法在我正在使用的组件上使用固定ID来执行此操作？任何人都可以解释我做错了什么吗？
最佳答案
And yes i did initialized it in constructor.
这正是问题所在。切勿使用 @FXML 注释初始化注入(inject) Controller 的字段。
如果您使用 @FXML 注释字段，FXMLLoader 将使用 FXML 文件中声明的实例来初始化该字段，并与字段名称(“consoleTextArea”匹配) ") 到 fx:id 属性。显然，这一切都发生在构造函数完成之后，但在调用 initialize() 方法之前。因此，您传递给 Console 构造函数的 consoleTextArea 与您在调用 initalize() 方法时最终得到的实例是不同的实例被调用(以及稍后调用事件处理程序时)。
要解决此问题，请完全删除构造函数，并在 initialize() 方法中初始化您需要的其他部分(即 FXML 中未定义的内容)。
类似于:
public class ConsoleController implements Initializable {
Thread t;
@FXML
private Label totalM;
@FXML
private Label freeM;
@FXML
private Label maxM;
@FXML
private TextArea consoleTextArea;
private Console console;
private PrintStream ps;
@Override
public void initialize(URL location, ResourceBundle resources) {
console = new Console(consoleTextArea);
ps = new PrintStream(console, true);
redirectOutput(ps);
t = new Thread(() -> {
while (true) {
try {
Platform.runLater(() -> {
updateMemInfo();
});
Thread.sleep(1000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
});
t.setPriority(Thread.MIN_PRIORITY);
t.setName("MemUpdateInfoThread");
t.setDaemon(true);
t.start();
}
// other methods as before...
}
关于JavaFX 重定向 System.out 流 TextArea，仅在不用作具有固定 ID 的 FXML 组件时才工作。为什么？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24915391/