How can I use a second Java class in my Android project?

Question

I'm developing an Android proyect and I get an "Unfortunately, Kana has stopped" error whenever I try to launch it. Kana is the name of my proyect. I'm newbie on Android Developing and I think the problem is that I instantiated an Object from a second java class on my MainActivity class and I guess that's not ok?

If that's the case, how can I use other Java classes apart from Activities (which need an XML file too)? I mean, my Java class isn't an Activity and I want it to run in background, just to use it's methods.

Can someone help me please? And excuse my poor english, if you need more info I'll try to explain it.

My activity:

package kana.menu;

import android.app.Activity;
import android.os.Bundle;
import android.widget.*;
import android.view.*;


public class KanaActivity extends Activity {
    /** Called when the activity is first created. */

    private TextView tv1;
    private EditText et1;
    private Mensaje m1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tv1=(TextView)findViewById(R.id.textView1);
        et1=(EditText)findViewById(R.id.editText1);
    }

    public void mensaje(View view){
        m1=new Mensaje("Hola");
        tv1.setText(m1.getMensaje()+et1.getText().toString());
    }


}

My java class I want to instantiate:

package kana.menu;

public class Mensaje {

private String msg="";

    public Mensaje(String mensaje){
        msg=mensaje;
    }

    public Mensaje(){}

    public void setMensaje(String mensaje){
        msg=mensaje;
    }
    public String getMensaje(){
        return this.msg;
    }
    public void borrarMensaje(){
        this.msg="";
    }

}

Post your code, and the stacktrace from your adb log. – Graham Borland Apr 25 '12 at 10:37 — Graham Borland, Apr 25 '12 at 10:37

score 1 · Accepted Answer · answered Apr 25 '12 at 10:39

1

It is totally okay to instantiate a java class from your activity. And if your java class isnt an activity then it wont need an XML file too. Whatever you are doing is perfectly legal and should work provided that it is implemented correctly. it would be great if you could share some code.

answered Apr 25 '12 at 10:39

Anurag Ramdasan

4,189
4
31
53

Oh really? That's good I guess but.. I don't know what may be the problem then... Here's the code, I hope you can help me. It's very simple: – Chocojosh Apr 25 '12 at 10:42
could you put the logcat here? – Anurag Ramdasan Apr 25 '12 at 14:15

score 0 · Answer 2 · answered Apr 25 '12 at 10:43

0

Maybe your app crashes due an Exception (Nullpointer?). As Anurag said, using "normal" java classes is completely legal, they dont need any xml or sth. If u could post us some code it'll be much more easier ;)

answered Apr 25 '12 at 10:43

Thkru

4,218
2
18
37

Excuse me It was my first question too.. had a little problems with editing lol – Chocojosh Apr 25 '12 at 10:58

How can I use a second Java class in my Android project?

2 Answers2