由于插入符號位置，文本欄位中的JavafxindexOutOfBoundsException-有解無憂

我正在構建一個小應用程式，TextField通過螢屏上的按鈕更新或洗掉文本。我已經利用這篇文章中的代碼來移動插入符號并添加文本。我可以在其中添加和洗掉字符，TextField但是當將n個字符添加到TextField然后洗掉nIndexOutOfBoundsException個字符時，當您嘗試添加另一個字符時發生，因為插入符號位置（當所有字符都被洗掉時）在應該為 0 時變為 1 .我不知道為什么它應該是0的時候變成了1。我在這里做錯了什么？

import java.util.concurrent.atomic.AtomicInteger;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        try {
            
            BorderPane root = new BorderPane();
            Pane panel = new Pane();
            VBox box = new VBox();
            TextField tf = new TextField();
            Button characterButton = new Button("a");
            Button deleteChar = new Button("delete");
            
            box.getChildren().addAll(tf, characterButton, deleteChar );
            panel.getChildren().add(box);
            root.getChildren().add(panel);
            
            Scene scene = new Scene(root,400,400);
            scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(scene);
            primaryStage.show();
            
            //handle caret pos
            AtomicInteger caretPos = new AtomicInteger();
            tf.caretPositionProperty().addListener((obs, oldVal, newVal) -> {
                System.out.println("newval"   newVal);
                if (tf.isFocused()) {
                    caretPos.set(newVal.intValue());
                    System.out.println("Innernewval"   newVal);
                }
            });
            //add character
            characterButton.setOnAction(( event) -> {
                Button btn = (Button)event.getSource();
                System.out.println("Pressed "   btn.getText()   " button");
                int pos = caretPos.get();
                tf.insertText(pos, btn.getText());
                tf.requestFocus();
                tf.positionCaret(pos 1);
                System.out.println("caretPos on add: "   caretPos.get());

            });
            //remove character
            deleteChar.setOnAction(( event) -> {
                Button btn = (Button)event.getSource();
                System.out.println("Pressed "   btn.getText()   " button");
                int newCaretPos = caretPos.get()-1;
                tf.deleteText(newCaretPos, caretPos.get());
                tf.requestFocus();
                tf.positionCaret(newCaretPos);   
                System.out.println("caretPos on delete: "   caretPos.get());
            });
            
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

uj5u.com熱心網友回復：

您的代碼無法編譯。你有一個catch沒有一個try。在下面的代碼中，我洗掉了 [orphan]catch塊。此外，您的樣式表，即檔案application.css與您的問題無關，因此為了使您問題中的代碼成為最小的、可重現的示例，我建議您洗掉該部分。它在下面的代碼中被注釋掉了。

我只有IndexOutOfBoundsException在caretPos為零并且按下deleteChar按鈕時才得到。因此，您只需添加處理該邊緣情況的代碼。在下面的代碼中，請參考注釋句柄洗掉后的部分，當 'caretPos' 為零時。

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        BorderPane root = new BorderPane();
        Pane panel = new Pane();
        VBox box = new VBox();
        TextField tf = new TextField();
        Button characterButton = new Button("a");
        Button deleteChar = new Button("delete");

        box.getChildren().addAll(tf, characterButton, deleteChar);
        panel.getChildren().add(box);
        root.getChildren().add(panel);

        Scene scene = new Scene(root, 400, 400);
//        scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.show();

        // handle caret pos
        AtomicInteger caretPos = new AtomicInteger();
        tf.caretPositionProperty().addListener((obs, oldVal, newVal) -> {
            System.out.println("newval: "   newVal);
            if (tf.isFocused()) {
                caretPos.set(newVal.intValue());
                System.out.println("Innernewval: "   newVal);
            }
        });
        // add character
        characterButton.setOnAction((event) -> {
            Button btn = (Button) event.getSource();
            System.out.println("Pressed "   btn.getText()   " button");
            int pos = caretPos.get();
            tf.insertText(pos, btn.getText());
            tf.requestFocus();
            tf.positionCaret(pos   1);
            System.out.println("caretPos on add: "   caretPos.get());

        });
        // remove character
        deleteChar.setOnAction((event) -> {
            Button btn = (Button) event.getSource();
            System.out.println("Pressed "   btn.getText()   " button");

            // Handle delete when 'caretPos' is zero.
            if (caretPos.get() == 0) {
                if (tf.getText().isEmpty()) {
                    return; // Nothing to delete.
                }
                else {
                    caretPos.set(1); // Ensure 'newCaretPos' will not be negative.
                }
            }

            int newCaretPos = caretPos.get() - 1;
            tf.deleteText(newCaretPos, caretPos.get());
            tf.requestFocus();
            tf.positionCaret(newCaretPos);
            caretPos.set(newCaretPos);
            System.out.println("caretPos on delete: "   caretPos.get());
        });
    }
}

編輯

你是對的。當我使用 JavaFX 8 運行您的代碼時，我確實重現了該問題。經過一些除錯，問題是當TextField包含單個字符并且您按deleteChar時，caretPositionProperty偵聽器不會運行，因此caretPosition不會更新并保持值 1（一）而不是 0（零）。

這個問題可能有很多解決方法。我選擇在事件處理程式if的行之后添加以下陳述句：System.out.println("caretPos on delete: " caretPos.get());deleteChar

if (tf.getText().isEmpty()) {
    caretPos.set(0);
}

For the sake of completeness, here is the code I used to debug the program.

import java.util.concurrent.atomic.AtomicInteger;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {
        try {
            
            BorderPane root = new BorderPane();
            Pane panel = new Pane();
            VBox box = new VBox();
            TextField tf = new TextField();
            Button characterButton = new Button("a");
            Button deleteChar = new Button("delete");
            
            box.getChildren().addAll(tf, characterButton, deleteChar );
            panel.getChildren().add(box);
            root.getChildren().add(panel);
            
            Scene scene = new Scene(root,400,400);
//            scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(scene);
            primaryStage.show();
            
            //handle caret pos
            AtomicInteger caretPos = new AtomicInteger();
            tf.caretPositionProperty().addListener((obs, oldVal, newVal) -> {
                System.out.println("newval"   newVal);
                if (tf.isFocused()) {
                    caretPos.set(newVal.intValue());
                    System.out.println("Innernewval"   newVal);
                }
            });
            //add character
            characterButton.setOnAction(( event) -> {
                Button btn = (Button)event.getSource();
                System.out.println("Pressed "   btn.getText()   " button");
                int pos = caretPos.get();
                System.out.println("###  DBUG  ### -> Adding: [Before 'insertText'] pos = "   pos);
                tf.insertText(pos, btn.getText());
                System.out.println("###  DBUG  ### -> Adding: [Before 'requestFocus'] pos = "   pos);
                tf.requestFocus();
                System.out.println("###  DBUG  ### -> Adding: [Before 'positionCaret'] pos = "   pos);
                tf.positionCaret(pos 1);
                System.out.println("caretPos on add: "   caretPos.get());
            });
            //remove character
            deleteChar.setOnAction(( event) -> {
                Button btn = (Button)event.getSource();
                System.out.println("Pressed "   btn.getText()   " button");
                int newCaretPos = caretPos.get()-1;
                System.out.println("###  DBUG  ### -> Deleting: [Before 'deleteText'] newCaretPos = "   newCaretPos);
                tf.deleteText(newCaretPos, caretPos.get());
                System.out.println("###  DBUG  ### -> Deleting: [Before 'requestFocus'] newCaretPos = "   newCaretPos);
                tf.requestFocus();
                System.out.println("###  DBUG  ### -> Deleting: [Before 'positionCaret'] newCaretPos = "   newCaretPos);
                tf.positionCaret(newCaretPos);   
                System.out.println("caretPos on delete: "   caretPos.get());
                if (tf.getText().isEmpty()) {
                    caretPos.set(0);
                }
            });
            
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

Here is the output when TextField contains a single character and I press deleteChar.

newval0
Pressed delete button
###  DBUG  ### -> Deleting: [Before 'deleteText'] newCaretPos = 0
###  DBUG  ### -> Deleting: [Before 'requestFocus'] newCaretPos = 0
###  DBUG  ### -> Deleting: [Before 'positionCaret'] newCaretPos = 0
caretPos on delete: 1

As you can see, the caretPositionProperty listener is not executed.

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標籤：按钮 javafx 文本域

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