Community: Developer Discussion Boards

monkforte

SORRY but how do i get the string entered in a textbox into a var?

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class DeriveMIDlet extends MIDlet implements CommandListener {

private Command runCommand;
private Command exitCommand;

private Display display;

public DeriveMIDlet() {
display = Display.getDisplay(this);

exitCommand = new Command("Exit", Command.EXIT, 1);
runCommand = new Command("Run", Command.SCREEN, 2);
}

public void startApp() {
TextBox input = new TextBox("app","", 256, 0);
input.addCommand(runCommand);
input.setCommandListener(this);
display.setCurrent(input);
}

public void pauseApp() { }

public void destroyApp(boolean unconditional) { }

public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
else if (c == runCommand) {
String function = input.text();
// -> HERE i need the input of the first text box in a variable
}
}
}

shmoove

Declare the TextBox as a class member, instead of inside startApp(), and then you use TextBox.getString() to get the string:

Code:

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class DeriveMIDlet extends MIDlet implements CommandListener {

  private Command runCommand;
  private Command exitCommand;

  private Display display;

  // declare the TextBox out here:
  TextBox input;

  public DeriveMIDlet() {
    display = Display.getDisplay(this);

    exitCommand = new Command("Exit", Command.EXIT, 1);
    runCommand = new Command("Run", Command.SCREEN, 2);
  }

  public void startApp() {
    // instead of declaring it here
    //TextBox input = new TextBox("app","", 256, 0);
    input = new TextBox("app","", 256, 0);
    input.addCommand(runCommand);
    input.setCommandListener(this);
    display.setCurrent(input);
  }

  public void pauseApp() { }

  public void destroyApp(boolean unconditional) { }

  public void commandAction(Command c, Displayable s) {
    if (c == exitCommand) {
      destroyApp(false);
      notifyDestroyed();
    }
    else if (c == runCommand) {
      // since input is now a class member field you can access
      // it from any member function
      String text = input.getString();
      System.out.println(text); // or whatever you want to do with it 
    }
  }
}

shmoove

niekvs

... and get "Java for dummies" ;)

monkforte

thanx

dont need java 4 dummies, but j2me for dummies ;)
but couldnt find a proper documentation/tutorial... at sun website, there seem to be various articles about several tools etc., but no single document providing a complete reference including things like methods for textbox as this getstring thing.

if somebody had a good document, i wouldnt have to ask that stpid questions :)

niekvs

you should probably download the API docs for J2ME from java.sun.com. There, you can find information about all classes and methods.

shmoove

Any J2ME SDK you download will usually have a docs subdirectory with all the API documentation.

shmoove

monkforte

thanks again. if you answer the following question, im completely satisfied for the moment:

why doesnt hitting the run command button in the following code force the prog to display the form Form (displayResult procedure)

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class DeriveMIDlet extends MIDlet implements CommandListener {

private Display display;
private Command runCommand;
private Command exitCommand;
TextField input;

public DeriveMIDlet() {
exitCommand = new Command("Exit", Command.EXIT, 1);
runCommand = new Command("Run", Command.SCREEN, 2);
}

public void startApp() {
display = Display.getDisplay(this);
Form main = new Form("Derivat0r");
TextField input = new TextField("enter function 2 derive","2*(3*x+x^2)^2", 256, 0);
main.append(input);
main.addCommand(runCommand);
display.setCurrent(main);
}

public void pauseApp() { }

public void destroyApp(boolean unconditional) { }

public void displayResult() {
display = Display.getDisplay(this);
Form form = new Form("working...");
TextField output = new TextField("result",Ableitung.ableiten(input.getString()),256,0);
form.append(output);
display.setCurrent(form);
}

public void commandAction(Command c, Displayable s) {
if (c == runCommand) {
displayResult();
}
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}

}
}

shmoove

Because you didn't set a listener for the commands:

Code:

public void startApp() {
  display = Display.getDisplay(this);
  Form main = new Form("Derivat0r");
  TextField input = new TextField("enter function 2 derive","2*(3*x+x^2)^2", 256, 0);
  main.append(input);
  main.addCommand(runCommand);
  // you're missing this line:
  main.setCommandListener(this);
  display.setCurrent(main);
}

Again, a quick browse through the docs and you would've discovered it by yourself.

shmoove

monkforte

what should i have searched for? if you dont know what exactly your problem is like, you also cant search for it.

now, everythings extremely fine EXCEPT for one thing:

every time I perform "String function = input.getString();" my emulator bashes me by throwing some NullPointerException... TextField "input" should contain a string, so im confused once more

niekvs

Looks like you messed up. You know, you really should learn Java first, because if you don't, you'll keep running into problems like this.

I'll give you a hint this time, instead of a solution :) Look for all the differences between the code in your last posting (the one you started with "thanks again. if you answer the following question, im completely satisfied for the moment", and the code that schmoove gave you.

You should find the answer to your question then...

Good luck!
-- Niek