Start the GUI

Getting the WindowBasedTextGUI object

Lanterna has a basic TextGUI interface and a slightly more extended WindowBasedTextGUI interface you will be using when working with the GUI system built-in. In reality though, there is only one concrete implementation at this point, MultiWindowTextGUI so there isn't really any case where you would use TextGUI over WindowBasedTextGUI.

To instantiate, you need a Screen object that the GUI will render too:

WindowBasedTextGUI gui = new MultiWindowTextGUI(screen);

Threading concerns

Usually GUI APIs have threading issues of some sort. Many simply give up and declare that all modifications have to be done on a designated "GUI thread". This is generally a reasonably approach and while Lanterna doesn't enforce it (internal API is synchronized on a best-effort basis), it's recommended. When you create the text GUI in your code, you can make a decision about if you want Lanterna to create its own GUI thread that will be responsible for all the drawing operations or if you want your own thread to do this. The managed GUI thread is slightly more complicated so in this guide we are going to use the latter. While most of the API remains the same (the separate GUI thread approach will require manually starting and stopping), whenever there are differences these will be pointed out.

By default, when you create a MultiWindowTextGUI like in the previous section, Lanterna will use the same-thread strategy.

Starting the GUI

Unlike Screen, the TextGUI interface doesn't have start or stop methods. It will simply use the Screen object you pass in as-is. Because of this, you'll want to start the screen before attempting to draw anything with the GUI.

Terminal term = new DefaultTerminalFactory().createTerminal();
Screen screen = new TerminalScreen(term);
WindowBasedTextGUI gui = new MultiWindowTextGUI(screen);
screen.startScreen();

// use GUI here until the GUI wants to exit

screen.stopScreen();

Next

Continue to Basic windows