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Selector.javaAPI DocJ2ME MIDP 2.06988Thu Nov 07 12:02:22 GMT 2002com.sun.midp.midlet

Selector

public class Selector extends javax.microedition.midlet.MIDlet implements CommandListener, Runnable
Selector provides a simple user interface to select MIDlets to run. It extracts the list of MIDlets from the attributes in the descriptor file and presents them to the user using the MIDlet-<n> name and icon if any. When the user selects a MIDlet an instance of the class indicated by MIDlet-<n> classname is created.

Fields Summary
private List
mlist
The List of all the MIDlets.
private Display
display
The Display.
private int
mcount
Number of midlets in minfo.
private boolean
exitAfterLaunch
should this MIDlet exit after launching another MIDlet
private MIDletInfo[]
minfo
MIDlet information, class, name, icon; one per MIDlet.
private Command
backCmd
the Command object to exit back to the MIDlet Suite Manager
private Command
launchCmd
the Command object for "Launch".
private int
selectedMidlet
Index of the selected MIDlet, starts at -1 for non-selected.
Constructors Summary
public Selector()
Create and initialize a new Selector MIDlet. The Display is retreived and the list of MIDlets read from the descriptor file.


                              
      
        this(true);
protected Selector(boolean exitFlag)
Create and initialize a new Selector MIDlet. The Display is retreived and the list of MIDlets read from the descriptor file.

param
exitFlag set this to true if the selector should exit after launching a MIDlet.

        exitAfterLaunch = exitFlag;
        display = Display.getDisplay(this); // TBD: is this value value here?
        mcount = 0;
        minfo = new MIDletInfo[20];
        readMIDletInfo();
Methods Summary
private voidaddMIDlet(MIDletInfo info)
Add a MIDlet to the list.

param
info MIDlet information to add to MIDlet

        if (mcount >= minfo.length) {
            MIDletInfo[] n = new MIDletInfo[mcount+4];
            System.arraycopy(minfo, 0, n, 0, mcount);
            minfo = n;
        }
        minfo[mcount++] = info;
public voidcommandAction(Command c, Displayable s)
Respond to a command issued on any Screen. The commands on list is Select and About. Select triggers the creation of the MIDlet of the same name. About puts up the copyright notice.

param
c command activiated by the user
param
s the Displayable the command was on.

	if ((s == mlist && c == List.SELECT_COMMAND) || (c == launchCmd)) {
            synchronized (this) {
                if (selectedMidlet != -1) {
                    // the previous selected MIDlet is being launched
                    return;
                }

                selectedMidlet = mlist.getSelectedIndex();
            }

            new Thread(this).start();
	} else if (c == backCmd) {
	    destroyApp(false);
	    notifyDestroyed();
            return;
        }
public voiddestroyApp(boolean unconditional)
Destroy cleans up. The only resource used is in the objects that will be reclaimed by the garbage collector.

param
unconditional is ignored; the Selector always destroys itself when requested.
public voidpauseApp()
Pause; there are no resources that need to be released.
private voidreadMIDletInfo()
Read in and create a MIDletInfor for each MIDlet-<n>

        for (int n = 1; n < 100; n++) {
            String nth = "MIDlet-"+ n;
            String attr = getAppProperty(nth);
            if (attr == null || attr.length() == 0)
                break;

            addMIDlet(new MIDletInfo(attr));
        }
public voidrun()
Launch a the select MIDlet.

        Scheduler scheduler = Scheduler.getScheduler();
        String classname = minfo[selectedMidlet].classname;

        try {
            scheduler.register(MIDletState.createMIDlet(classname));

            if (exitAfterLaunch) {
                // exit
                destroyApp(false);
                notifyDestroyed();
                return;
            }

            // Give the new MIDlet the screen by setting current to null
            display.setCurrent(null);

            // let another MIDlet be selected after MIDlet ends
            selectedMidlet = -1;
            return;
        } catch (Exception ex) {
            StringBuffer sb = new StringBuffer()
                .append(minfo[selectedMidlet].name)
                .append(", ")
                .append(classname)
                .append("\n")
                .append(Resource.getString("Exception"))
                .append(": ")
                .append(ex.toString());

            Alert a = new Alert(Resource.getString("Cannot start: "), 
                                sb.toString(), null, null);
            System.out.println("Unable to create MIDlet " + classname);
            ex.printStackTrace();
            display.setCurrent(a, mlist);

            // let another MIDlet be selected after the alert
            selectedMidlet = -1;
            return;
        }
private voidsetupList()
Read the set of MIDlet names, icons and classes Fill in the list.

        if (mlist == null) {
            mlist = new List(Resource.getString("Select one to launch:"), 
                             Choice.IMPLICIT);

	    // Add each midlet
	    for (int i = 0; i < mcount; i++) {
		Image icon = null;
		if (minfo[i].icon != null) {
		    try { 
		        icon = Image.createImage(minfo[i].icon);
		    } catch (java.io.IOException noImage) {
			// TBD: use a default ICON of the app has none.
		    }
		}
		mlist.append(" " + minfo[i].name, icon);
	    }
	}
public voidstartApp()
Start puts up a List of the MIDlets found in the descriptor file.

        setupList();
        mlist.addCommand(launchCmd);

        if (exitAfterLaunch) {
            mlist.addCommand(backCmd);
        }

        mlist.setCommandListener(this); // Listen for the selection

        display.setCurrent(mlist);