Java jtextarea перенос строк
Здравствуйте, Vlad_, Вы писали:
V_>Подскажите плиз, как в JTextArea сделать перенос строк (word wrap)
The following code, taken from TextSamplerDemo.java, demonstrates initializing an editable text area. The text area uses the specified italic font, and wraps lines between words.
JTextArea textArea = new JTextArea( "This is an editable JTextArea. " + "A text area is a \"plain\" text component, " + "which means that although it can display text " + "in any font, all of the text is in the same font." ); textArea.setFont(new Font("Serif", Font.ITALIC, 16)); textArea.setLineWrap(true); textArea.setWrapStyleWord(true);B>The following code, taken from TextSamplerDemo.java, demonstrates initializing an editable text area. The text area uses the specified italic font, and wraps lines between words.
B>JTextArea textArea = new JTextArea( B> "This is an editable JTextArea. " + B> "A text area is a \"plain\" text component, " + B> "which means that although it can display text " + B> "in any font, all of the text is in the same font." B>); B>textArea.setFont(new Font("Serif", Font.ITALIC, 16)); B>textArea.setLineWrap(true); B>textArea.setWrapStyleWord(true); B>Учимся программировать на Java с нуля
Иногда при работе программы возникает необходимость ввести несколько строк. Для этого применяется компонент JTextArea. Поместив данный компонент в свою программу, разработчик предоставляет пользователю возможность вводить любое количество текста, разделяя строки нажатием клавиши Enter>.
Каждая строка заканчивается символом ‘\n‘, как это предусмотрено в языке Java. Пример работы текстовой области показан на рис.1.
В конструкторе компонента JTextArea указывается количество строк и их длина. Например:
Параметр, задающий количество символов в строке, действует так же, как и для поля редактирования, его значение рекомендуется немного завысить. Пользователь не органичен количеством строк и их длинной. Если длина строки или чисто строк выйдет за пределы заданных параметров, текст будет прокручиваться в окне.
Для изменения длины строк можно применять метод setColumns(), а для изменения их количества — метод setRows(). Эти параметры задают лишь рекомендуемые размеры — диспетчер компоновки может самостоятельно увеличивать или уменьшать размеры поля редактирования.
Рис.1. Текстовая область
Если пользователь ввел больше текста, чем умещается в текстовой области, про произойдет отсечение. Этого можно избежать, установив автоматический перенос строки(line-wrapping).
Автоматический перенос проявляется лишь визуально. Текст хранящийся в документе, изменен не будет — в него не вставляются символы ‘\n’.
В пакете Swing текстовая область не имеет полос прокрутки. Если они необходимы, текстовую область следует включить в панель прокрутки(scroll pane):
Теперь панель прокрутки управляет представлением текстовой области. Полоса прокрутки автоматически появляется, когда текст выходит из рамки отведенной для него области, и исчезает, когда «лишняя» часть текста удаляется. Прокрутка поддерживается панелью прокрутки — сама программа не обязана обрабатывать события, связанные с ней.
Это универсальный механизм, который работает с любым компонентом, а не только с текстовыми областями. Чтобы добавить линейки прокрутки к компоненту, поместите его в панель прокрутки.
Программа которая приведена ниже демонстрирует различные текстовые компоненты. Эта программа отображает текстовое поле, поле пароля и текстовую область с линейками прокрутки. Текстовое поле и поле пароля снабжены метками. Чтобы вставить предложение в конец текста, щелкните на кнопке Insert(Вставить).
Вот собственно код программы:
How to Use Text Areas
The JTextArea class provides a component that displays multiple lines of text and optionally allows the user to edit the text. If you need to obtain only one line of input from the user, you should use a text field. If you want the text area to display its text using multiple fonts or other styles, you should use an editor pane or text pane. If the displayed text has a limited length and is never edited by the user, use a label.
Many of the Tutorial’s examples use uneditable text areas to display program output. Here is a picture of an example called TextDemo that enables you to type text using a text field (at the top) and then appends the typed text to a text area (underneath).
Click the Launch button to run TextDemo using Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.
You can find the entire code for this program in TextDemo.java . The following code creates and initializes the text area:
textArea = new JTextArea(5, 20); JScrollPane scrollPane = new JScrollPane(textArea); textArea.setEditable(false);
The two arguments to the JTextArea constructor are hints as to the number of rows and columns, respectively, that the text area should display. The scroll pane that contains the text area pays attention to these hints when determining how big the scroll pane should be.
Without the creation of the scroll pane, the text area would not automatically scroll. The JScrollPane constructor shown in the preceding snippet sets up the text area for viewing in a scroll pane, and specifies that the scroll pane’s scroll bars should be visible when needed. See How to Use Scroll Panes if you want further information.
Text areas are editable by default. The code setEditable(false) makes the text area uneditable. It is still selectable and the user can copy data from it, but the user cannot change the text area’s contents directly.
The following code adds text to the text area. Note that the text system uses the ‘\n’ character internally to represent newlines; for details, see the API documentation for DefaultEditorKit .
private final static String newline = "\n"; . textArea.append(text + newline);
Unless the user has moved the caret (insertion point) by clicking or dragging in the text area, the text area automatically scrolls so that the appended text is visible. You can force the text area to scroll to the bottom by moving the caret to the end of the text area after the call to append :
textArea.setCaretPosition(textArea.getDocument().getLength());
Customizing Text Areas
You can customize text areas in several ways. For example, although a given text area can display text in only one font and color, you can set which font and color it uses. This customization option can be performed on any component. You can also determine how the text area wraps lines and the number of characters per tab. Finally, you can use the methods that the JTextArea class inherits from the JTextComponent class to set properties such as the caret, support for dragging, or color selection.
The following code taken from TextSamplerDemo.java demonstrates initializing an editable text area. The text area uses the specified italic font, and wraps lines between words.
JTextArea textArea = new JTextArea( "This is an editable JTextArea. " + "A text area is a \"plain\" text component, " + "which means that although it can display text " + "in any font, all of the text is in the same font." ); textArea.setFont(new Font("Serif", Font.ITALIC, 16)); textArea.setLineWrap(true); textArea.setWrapStyleWord(true); By default, a text area does not wrap lines that are too long for the display area. Instead, it uses one line for all the text between newline characters and if the text area is within a scroll pane allows itself to be scrolled horizontally. This example turns line wrapping on with a call to the setLineWrap method and then calls the setWrapStyleWord method to indicate that the text area should wrap lines at word boundaries rather than at character boundaries.
To provide scrolling capability, the example puts the text area in a scroll pane.
JScrollPane areaScrollPane = new JScrollPane(textArea); areaScrollPane.setVerticalScrollBarPolicy( JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); areaScrollPane.setPreferredSize(new Dimension(250, 250));
You might have noticed that the JTextArea constructor used in this example does not specify the number of rows or columns. Instead, the code limits the size of the text area by setting the scroll pane’s preferred size.
Another Example: TextAreaDemo
The TextAreaDemo example introduces an editable text area with a special feature a word completion function. As the user types in words, the program suggests hints to complete the word whenever the program’s vocabulary contains a word that starts with what has been typed. Here is a picture of the TextAreaDemo application.
Click the Launch button to run TextAreaDemo using Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.
You can find the entire code for this program in TextAreaDemo.java .
This example provides a scrolling capacity for the text area with the default scroll bar policy. By default, the vertical scroll bar only appears when the display area is entirely filled with text and there is no room to append new words. You can provide a scroll pane of this type with the following code:
textArea.setWrapStyleWord(true); jScrollPane1 = new JScrollPane(textArea);
As mentioned above, the text area is editable. You can play with the text area by typing and pasting text, or by deleting some parts of text or the entire content. Also try using standard key bindings for editing text within the text area.
Now explore how the word completion function is implemented. Type in a word like «Swing» or «special». As soon as you have typed «sw» the program shows a possible completion «ing» highlighted in light-blue. Press Enter to accept the completion or continue typing.
The following code adds a document listener to the text area’s document:
textArea.getDocument().addDocumentListener(this);
When you started typing a word, the insertUpdate method checks whether the program’s vocabulary contains the typed prefix. Once a completion for the prefix is found, a call to the invokeLater method submits a task for changing the document later. It is important to remember that you cannot modify the document from within the document event notification, otherwise you will get an exception. Examine the following code below.
String prefix = content.substring(w + 1).toLowerCase(); int n = Collections.binarySearch(words, prefix); if (n < 0 && -n > else < // Nothing found mode = Mode.INSERT; >
The code shown in bold illustrates how the selection is created. The caret is first set to the end of the complete word, then moved back to a position after the last character typed. The moveCaretPosition method not only moves the caret to a new position but also selects the text between the two positions. The completion task is implemented with the following code:
private class CompletionTask implements Runnable < String completion; int position; CompletionTask(String completion, int position) < this.completion = completion; this.position = position; >public void run() < textArea.insert(completion, position); textArea.setCaretPosition(position + completion.length()); textArea.moveCaretPosition(position); mode = Mode.COMPLETION; > >
The Text Area API
The following tables list the commonly used JTextArea constructors and methods. Other methods you are likely to call are defined in JTextComponent , and listed in The Text Component API.
You might also invoke methods on a text area that it inherits from its other ancestors, such as setPreferredSize , setForeground , setBackground , setFont , and so on. See The JComponent Class for tables of commonly used inherited methods.
The API for using text areas includes the following categories:
Examples That Use Text Areas
This table lists examples that use text areas and points to where those examples are described.
| Example | Where Described | Notes |
|---|---|---|
| TextDemo | This section | An application that appends user-entered text to a text area. |
| TextAreaDemo | This section | An application that has a text area with a word completion function. |
| TextSamplerDemo | Using Text Components | Uses one of each Swing text components. |
| HtmlDemo | How to Use HTML in Swing Components | A text area that enables the user to type HTML code to be displayed in a label. |
| BasicDnD | Introduction to DnD | Demonstrates built-in drag-and-drop functionality of several Swing components, including text areas. |
| FocusConceptsDemo | How to Use the Focus Subsystem | Demonstrates how focus works using a few components that include a text area. |