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Class ptplot.PlotLive

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Container
                   |
                   +----java.awt.Panel
                           |
                           +----ptplot.PlotBox
                                   |
                                   +----ptplot.Plot
                                           |
                                           +----ptplot.PlotLive

public abstract class PlotLive

extends Plot

implements Runnable

This class is abstract, so it must be used by creating a derived class. To use it, create a derived class with init() and addPoints() methods. The init() method can call methods in the Plot or PlotBox classes (both of which are base classes) to set the static properties of the graph, such as the title, axis ranges, and axis labels. The addPoints() method should call addPoint() of the Plot base class to dynamically add points to the plot. This method is called within a thread separate from the applet thread.

The init() method must call super.init() somewhere in its body; along with general initialization, this reads a file given by a URL if the dataurl applet parameter is specified. Thus, the initial configuration can be specified in a separate file rather than in Java code.

Version:

@(#)PlotLive.java 1.28 10/25/97

Author:

Edward A. Lee, Christopher Hylands

PlotLive()

action(Event, Object)

Handle button presses to enable or disable plotting. Deprecated.

addPoints()

Redefine in derived classes to add points to the plot.

makeButtons()

Create a start and stop buttons, by which the user can invoke enable() and disable.

run()

This is the body of a thread that monitors which of the start or stop buttons have been pushed most recently, or which of the enable() or disable() methods has been called most recently, to determine whether to patiently wait or to call the addPoints() method.

setPlotting(boolean)

If plotting is set to true, then we plot.

start()

Start the widget.

stop()

Stop the widget.

 public PlotLive()

 public boolean action(Event evt,
                       Object arg)

Note: action() is deprecated. As of JDK1.1 in java.awt.component but we need to compile under 1.0.2 for netscape3.x compatibility.

Handle button presses to enable or disable plotting.

Overrides:

action in class PlotBox

 public abstract synchronized void addPoints()

Redefine in derived classes to add points to the plot. Adding many points at once will make the plot somewhat faster because the thread yields between calls to this method. However, the plot will also be somewhat less responsive to user inputs such as zooming, filling, or stopping.

 public void makeButtons()

Create a start and stop buttons, by which the user can invoke enable() and disable. Alternatively, a derived class might invoke these directly and dispense with the buttons. This should be called within the init() method in derived classes.

 public void run()

This is the body of a thread that monitors which of the start or stop buttons have been pushed most recently, or which of the enable() or disable() methods has been called most recently, to determine whether to patiently wait or to call the addPoints() method. Between calls to addPoints(), it calls Thread.yield() so that the thread does not hog all the resources. This somewhat slows down execution, so derived classes may wish to plot quite a few points in their addPoints() method, if possible. However, plotting more points at once may also decrease the responsiveness of the user interface.

 public void setPlotting(boolean plotting)

If plotting is set to true, then we plot.

 public void start()

Start the widget. It creates a thread to plot live data, if this has not been already done. However, we don't actually start plotting until either the start button is called, or setPlotting(true) is called.

Overrides:

start in class Plot

 public void stop()

Stop the widget.

Overrides:

stop in class Plot

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