Text areas

Bruce Eckel's Thinking in Java Contents | Prev | Next

A TextArea is like a TextField except that it can have multiple lines and has significantly more functionality. In addition to what you can do with a TextField, you can append text and insert or replace text at a given location. It seems like this functionality could be useful for TextField as well, so it’s a little confusing to try to detect how the distinction is made. You might think that if you want TextArea functionality everywhere you can simply use a one line TextArea in places where you would otherwise use a TextField. In Java 1.0, you also got scroll bars with a TextArea even when they weren’t appropriate; that is, you got both vertical and horizontal scroll bars for a one line TextArea. In Java 1.1 this was remedied with an extra constructor that allows you to select which scroll bars (if any) are present. The following example shows only the Java 1.0 behavior, in which the scrollbars are always on. Later in the chapter you’ll see an example that demonstrates Java 1.1 TextAreas.

//: TextArea1.java
// Using the text area control
import java.awt.*;
import java.applet.*;
 
public class TextArea1 extends Applet {
  Button b1 = new Button("Text Area 1");
  Button b2 = new Button("Text Area 2");
  Button b3 = new Button("Replace Text");
  Button b4 = new Button("Insert Text");
  TextArea t1 = new TextArea("t1", 1, 30);
  TextArea t2 = new TextArea("t2", 4, 30);
  public void init() {
    add(b1);
    add(t1);
    add(b2);
    add(t2);
    add(b3);
    add(b4);
  }
  public boolean action (Event evt, Object arg) {
    if(evt.target.equals(b1))
      getAppletContext().showStatus(t1.getText());
    else if(evt.target.equals(b2)) {
      t2.setText("Inserted by Button 2");
      t2.appendText(": " + t1.getText());
      getAppletContext().showStatus(t2.getText());
    }
    else if(evt.target.equals(b3)) {
      String s = " Replacement ";
      t2.replaceText(s, 3, 3 + s.length());
    }
    else if(evt.target.equals(b4))
      t2.insertText(" Inserted ", 10);
    // Let the base class handle it:
    else 
      return super.action(evt, arg);
    return true; // We've handled it here
  }
} ///:~ 

There are several different TextArea constructors, but the one shown here gives a starting string and the number of rows and columns. The different buttons show getting, appending, replacing, and inserting text.



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • On-demand Event Event Date: September 10, 2014 Modern mobile applications connect systems-of-engagement (mobile apps) with systems-of-record (traditional IT) to deliver new and innovative business value. But the lifecycle for development of mobile apps is also new and different. Emerging trends in mobile development call for faster delivery of incremental features, coupled with feedback from the users of the app "in the wild." This loop of continuous delivery and continuous feedback is how the best mobile …

  • Packaged application development teams frequently operate with limited testing environments due to time and labor constraints. By virtualizing the entire application stack, packaged application development teams can deliver business results faster, at higher quality, and with lower risk.

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds