Writer implementation which provides a means for writing directly to a JTextArea.
1
2 import java.io.Writer;
3 import java.io.IOException;
4
5 import javax.swing.JTextArea;
6
7 /** A implementation of the java.io.Writer class which facilitates writing to a JTextArea via a stream.
8
9 <p><b>Note:</b> There appears to be bug in the Macintosh implementation of
10 the JDK 1.1 where a PrintWriter writing to this class will not include the
11 correct line feeds for display in a JTextArea. There is a simple test of
12 the "java.version" system property which, if it starts with the String "1.1"
13 will cause newlines to be written each time the buffer is flushed.</p>
14
15 @author Anthony Eden
16 */
17
18 public class JTextAreaWriter extends Writer{
19
20 private boolean closed = false;
21 private JTextArea textArea;
22 private StringBuffer buffer;
23
24 /** Constructor.
25
26 @param textArea The JTextArea to write to.
27 */
28
29 public JTextAreaWriter(JTextArea textArea){
30 setTextArea(textArea);
31 }
32
33 /** Set the JTextArea to write to.
34
35 @param textArea The JTextArea
36 */
37
38 public void setTextArea(JTextArea textArea){
39 if(textArea == null){
40 throw new IllegalArgumentException("The text area must not be null.");
41 }
42 this.textArea = textArea;
43 }
44
45 /** Close the stream. */
46
47 public void close(){
48 closed = true;
49 }
50
51 /** Flush the data that is currently in the buffer.
52
53 @throws IOException
54 */
55
56 public void flush() throws IOException{
57 if(closed){
58 throw new IOException("The stream is not open.");
59 }
60 // the newline character should not be necessary. The PrintWriter
61 // should autmatically put the newline, but it doesn't seem to work
62 textArea.append(getBuffer().toString());
63 if(System.getProperty("java.version").startsWith("1.1")){
64 textArea.append("\n");
65 }
66 textArea.setCaretPosition(textArea.getDocument().getLength());
67 buffer = null;
68 }
69
70 /** Write the given character array to the output stream.
71
72 @param charArray The character array
73 @throws IOException
74 */
75
76 public void write(char[] charArray) throws IOException{
77 write(charArray, 0, charArray.length);
78 }
79
80 /** Write the given character array to the output stream beginning from
81 the given offset and proceeding to until the given length is reached.
82
83 @param charArray The character array
84 @param offset The start offset
85 @param length The length to write
86 @throws IOException
87 */
88
89 public void write(char[] charArray, int offset, int length) throws IOException{
90 if(closed){
91 throw new IOException("The stream is not open.");
92 }
93 getBuffer().append(charArray, offset, length);
94 }
95
96 /** Write the given character to the output stream.
97
98 @param c The character
99 @throws IOException
100 */
101
102 public void write(int c) throws IOException{
103 if(closed){
104 throw new IOException("The stream is not open.");
105 }
106 getBuffer().append((char)c);
107 }
108
109 /** Write the given String to the output stream.
110
111 @param string The String
112 @throws IOException
113 */
114
115 public void write(String string) throws IOException{
116 if(closed){
117 throw new IOException("The stream is not open.");
118 }
119 getBuffer().append(string);
120 }
121
122 /** Write the given String to the output stream beginning from the given offset
123 and proceeding to until the given length is reached.
124
125 @param string The String
126 @param offset The start offset
127 @param length The length to write
128 @throws IOException
129 */
130
131 public void write(String string, int offset, int length) throws IOException{
132 if(closed){
133 throw new IOException("The stream is not open.");
134 }
135 getBuffer().append(string.substring(offset, length));
136 }
137
138 // protected methods
139
140 /** Get the StringBuffer which holds the data prior to writing via
141 a call to the <code>flush()
method. This method should
never return null.
@return A StringBuffer
*/
protected StringBuffer getBuffer(){
if(buffer == null){
buffer = new StringBuffer();
}
return buffer;
}
}
