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Java javax.swing Class JTextArea（JDK8）

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Java™ Platform
Standard Ed. 8
javax.swing

Class JTextArea

  • All Implemented Interfaces:
    ImageObserver, MenuContainer, Serializable, Accessible, Scrollable 

    public class JTextArea
extends JTextComponent
    A JTextArea is a multi-line area that displays plain text. It is intended to be a lightweight component that provides source compatibility with the java.awt.TextArea class where it can reasonably do so. You can find information and examples of using all the text components in Using Text Components, a section in The Java Tutorial.

    This component has capabilities not found in the java.awt.TextArea class. The superclass should be consulted for additional capabilities. Alternative multi-line text classes with more capabilities are JTextPane and JEditorPane.

    The java.awt.TextArea internally handles scrolling. JTextArea is different in that it doesn't manage scrolling, but implements the swing Scrollable interface. This allows it to be placed inside a JScrollPane if scrolling behavior is desired, and used directly if scrolling is not desired.

    The java.awt.TextArea has the ability to do line wrapping. This was controlled by the horizontal scrolling policy. Since scrolling is not done by JTextArea directly, backward compatibility must be provided another way. JTextArea has a bound property for line wrapping that controls whether or not it will wrap lines. By default, the line wrapping property is set to false (not wrapped).

    java.awt.TextArea has two properties rows and columns that are used to determine the preferred size. JTextArea uses these properties to indicate the preferred size of the viewport when placed inside a JScrollPane to match the functionality provided by java.awt.TextArea. JTextArea has a preferred size of what is needed to display all of the text, so that it functions properly inside of a JScrollPane. If the value for rows or columns is equal to zero, the preferred size along that axis is used for the viewport preferred size along the same axis.

    The java.awt.TextArea could be monitored for changes by adding a TextListener for TextEvents. In the JTextComponent based components, changes are broadcasted from the model via a DocumentEvent to DocumentListeners. The DocumentEvent gives the location of the change and the kind of change if desired. The code fragment might look something like:

        DocumentListener myListener = ??;
    JTextArea myArea = ??;
    myArea.getDocument().addDocumentListener(myListener);
    Newlines
    For a discussion on how newlines are handled, see DefaultEditorKit.

    Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

    Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.

    See Also:
    JTextPane, JEditorPane

    • Constructor Detail

      • JTextArea

        public JTextArea()
        Constructs a new TextArea. A default model is set, the initial string is null, and rows/columns are set to 0.

      • JTextArea

        public JTextArea(String text)
        Constructs a new TextArea with the specified text displayed. A default model is created and rows/columns are set to 0.
        Parameters:
        text - the text to be displayed, or null

      • JTextArea

        public JTextArea(int rows,
                 int columns)
        Constructs a new empty TextArea with the specified number of rows and columns. A default model is created, and the initial string is null.
        Parameters:
        rows - the number of rows >= 0
        columns - the number of columns >= 0
        Throws:
        IllegalArgumentException - if the rows or columns arguments are negative.

      • JTextArea

        public JTextArea(String text,
                 int rows,
                 int columns)
        Constructs a new TextArea with the specified text and number of rows and columns. A default model is created.
        Parameters:
        text - the text to be displayed, or null
        rows - the number of rows >= 0
        columns - the number of columns >= 0
        Throws:
        IllegalArgumentException - if the rows or columns arguments are negative.

      • JTextArea

        public JTextArea(Document doc)
        Constructs a new JTextArea with the given document model, and defaults for all of the other arguments (null, 0, 0).
        Parameters:
        doc - the model to use

      • JTextArea

        public JTextArea(Document doc,
                 String text,
                 int rows,
                 int columns)
        Constructs a new JTextArea with the specified number of rows and columns, and the given model. All of the constructors feed through this constructor.
        Parameters:
        doc - the model to use, or create a default one if null
        text - the text to be displayed, null if none
        rows - the number of rows >= 0
        columns - the number of columns >= 0
        Throws:
        IllegalArgumentException - if the rows or columns arguments are negative.

    • Method Detail

      • createDefaultModel

        protected Document createDefaultModel()
        Creates the default implementation of the model to be used at construction if one isn't explicitly given. A new instance of PlainDocument is returned.
        Returns:
        the default document model

      • setTabSize

        public void setTabSize(int size)
        Sets the number of characters to expand tabs to. This will be multiplied by the maximum advance for variable width fonts. A PropertyChange event ("tabSize") is fired when the tab size changes.
        Parameters:
        size - number of characters to expand to
        See Also:
        getTabSize()

      • getTabSize

        public int getTabSize()
        Gets the number of characters used to expand tabs. If the document is null or doesn't have a tab setting, return a default of 8.
        Returns:
        the number of characters

      • setLineWrap

        public void setLineWrap(boolean wrap)
        Sets the line-wrapping policy of the text area. If set to true the lines will be wrapped if they are too long to fit within the allocated width. If set to false, the lines will always be unwrapped. A PropertyChange event ("lineWrap") is fired when the policy is changed. By default this property is false.
        Parameters:
        wrap - indicates if lines should be wrapped
        See Also:
        getLineWrap()

      • getLineWrap

        public boolean getLineWrap()
        Gets the line-wrapping policy of the text area. If set to true the lines will be wrapped if they are too long to fit within the allocated width. If set to false, the lines will always be unwrapped.
        Returns:
        if lines will be wrapped

      • setWrapStyleWord

        public void setWrapStyleWord(boolean word)
        Sets the style of wrapping used if the text area is wrapping lines. If set to true the lines will be wrapped at word boundaries (whitespace) if they are too long to fit within the allocated width. If set to false, the lines will be wrapped at character boundaries. By default this property is false.
        Parameters:
        word - indicates if word boundaries should be used for line wrapping
        See Also:
        getWrapStyleWord()

      • getWrapStyleWord

        public boolean getWrapStyleWord()
        Gets the style of wrapping used if the text area is wrapping lines. If set to true the lines will be wrapped at word boundaries (ie whitespace) if they are too long to fit within the allocated width. If set to false, the lines will be wrapped at character boundaries.
        Returns:
        if the wrap style should be word boundaries instead of character boundaries
        See Also:
        setWrapStyleWord(boolean)

      • getLineOfOffset

        public int getLineOfOffset(int offset)
                    throws BadLocationException
        Translates an offset into the components text to a line number.
        Parameters:
        offset - the offset >= 0
        Returns:
        the line number >= 0
        Throws:
        BadLocationException - thrown if the offset is less than zero or greater than the document length.

      • getLineCount

        public int getLineCount()
        Determines the number of lines contained in the area.
        Returns:
        the number of lines > 0

      • getLineStartOffset

        public int getLineStartOffset(int line)
                       throws BadLocationException
        Determines the offset of the start of the given line.
        Parameters:
        line - the line number to translate >= 0
        Returns:
        the offset >= 0
        Throws:
        BadLocationException - thrown if the line is less than zero or greater or equal to the number of lines contained in the document (as reported by getLineCount).

      • getLineEndOffset

        public int getLineEndOffset(int line)
                     throws BadLocationException
        Determines the offset of the end of the given line.
        Parameters:
        line - the line >= 0
        Returns:
        the offset >= 0
        Throws:
        BadLocationException - Thrown if the line is less than zero or greater or equal to the number of lines contained in the document (as reported by getLineCount).

      • append

        public void append(String str)
        Appends the given text to the end of the document. Does nothing if the model is null or the string is null or empty.
        Parameters:
        str - the text to insert
        See Also:
        insert(java.lang.String, int)

      • replaceRange

        public void replaceRange(String str,
                         int start,
                         int end)
        Replaces text from the indicated start to end position with the new text specified. Does nothing if the model is null. Simply does a delete if the new string is null or empty.
        Parameters:
        str - the text to use as the replacement
        start - the start position >= 0
        end - the end position >= start
        Throws:
        IllegalArgumentException - if part of the range is an invalid position in the model
        See Also:
        insert(java.lang.String, int)

      • getRows

        public int getRows()
        Returns the number of rows in the TextArea.
        Returns:
        the number of rows >= 0

      • setRows

        public void setRows(int rows)
        Sets the number of rows for this TextArea. Calls invalidate() after setting the new value.
        Parameters:
        rows - the number of rows >= 0
        Throws:
        IllegalArgumentException - if rows is less than 0
        See Also:
        getRows()

      • getRowHeight

        protected int getRowHeight()
        Defines the meaning of the height of a row. This defaults to the height of the font.
        Returns:
        the height >= 1

      • getColumns

        public int getColumns()
        Returns the number of columns in the TextArea.
        Returns:
        number of columns >= 0

      • setColumns

        public void setColumns(int columns)
        Sets the number of columns for this TextArea. Does an invalidate() after setting the new value.
        Parameters:
        columns - the number of columns >= 0
        Throws:
        IllegalArgumentException - if columns is less than 0
        See Also:
        getColumns()

      • getColumnWidth

        protected int getColumnWidth()
        Gets column width. The meaning of what a column is can be considered a fairly weak notion for some fonts. This method is used to define the width of a column. By default this is defined to be the width of the character m for the font used. This method can be redefined to be some alternative amount.
        Returns:
        the column width >= 1

      • setFont

        public void setFont(Font f)
        Sets the current font. This removes cached row height and column width so the new font will be reflected, and calls revalidate().
        Overrides:
        setFont in class JComponent
        Parameters:
        f - the font to use as the current font
        See Also:
        Component.getFont()

      • paramString

        protected String paramString()
        Returns a string representation of this JTextArea. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.
        Overrides:
        paramString in class JTextComponent
        Returns:
        a string representation of this JTextArea.

      • getScrollableTracksViewportWidth

        public boolean getScrollableTracksViewportWidth()
        Returns true if a viewport should always force the width of this Scrollable to match the width of the viewport. This is implemented to return true if the line wrapping policy is true, and false if lines are not being wrapped.
        Specified by:
        getScrollableTracksViewportWidth in interface Scrollable
        Overrides:
        getScrollableTracksViewportWidth in class JTextComponent
        Returns:
        true if a viewport should force the Scrollables width to match its own.

      • getScrollableUnitIncrement

        public int getScrollableUnitIncrement(Rectangle visibleRect,
                                      int orientation,
                                      int direction)
        Components that display logical rows or columns should compute the scroll increment that will completely expose one new row or column, depending on the value of orientation. This is implemented to use the values returned by the getRowHeight and getColumnWidth methods.

        Scrolling containers, like JScrollPane, will use this method each time the user requests a unit scroll.

        Specified by:
        getScrollableUnitIncrement in interface Scrollable
        Overrides:
        getScrollableUnitIncrement in class JTextComponent
        Parameters:
        visibleRect - the view area visible within the viewport
        orientation - Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL.
        direction - Less than zero to scroll up/left, greater than zero for down/right.
        Returns:
        The "unit" increment for scrolling in the specified direction
        Throws:
        IllegalArgumentException - for an invalid orientation
        See Also:
        JScrollBar.setUnitIncrement(int), getRowHeight(), getColumnWidth()

      • getAccessibleContext

        public AccessibleContext getAccessibleContext()
        Gets the AccessibleContext associated with this JTextArea. For JTextAreas, the AccessibleContext takes the form of an AccessibleJTextArea. A new AccessibleJTextArea instance is created if necessary.
        Specified by:
        getAccessibleContext in interface Accessible
        Overrides:
        getAccessibleContext in class JTextComponent
        Returns:
        an AccessibleJTextArea that serves as the AccessibleContext of this JTextArea
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Java™ Platform
Standard Ed. 8

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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2022, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.

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