java 灯笼无法从终端读取输入

Question

I have problems using the readInput() method from the lanterna package. My codefraction

    Terminal terminal = TerminalFacade.createSwingTerminal();
    terminal.enterPrivateMode();
    Key key = terminal.readInput();
    if(key.getKind()==Key.Kind.Escape){
    terminal.moveCursor(6, 6);
    terminal.putCharacter('X');

doesn't allow me to do any input in the terminal and therefore creates a nullpointerexception when checking for key.getKind. Does anybody have an idea why this happens?

Answer 1

The readInput method is non-blocking. It means that it will not hang until a input is found (as ie Scanner does). So you will need your own "blocking method" which waits for an input:

Key key = terminal.readInput();
while(key == null) {
    Thread.sleep(5); //whatever low value
    key = terminal.readInput();
}
// here key will not be null, so no NullPointerException

Answer 2

I would like to add an updated answer here. As of lanterna 3.1.1, the readInput() method is now blocking. This means that it will hang until a user inputs.

You should use pollInput() instead, as this is the new non-blocking method.