Android Change textView text from another method/class

Question

After a click on button1, another layout and another class gets called. Now I want to change the text of textView out of class 2 which results in an app crash with java.lang.NullPointerException

important parts of Class 1

public static TextView A;
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

[button stuff in class 1]

 setContentView(R.layout.raten);
                      final    TextView A = (TextView) findViewById(R.id.A); //the textview I wanna chage
                 max = 10;
                      Easy easy = new Easy(); // the other class
                      easy.e();

[now the method in class 1 that should change the text]

    public static void Tx(int i)
    {
 A.setText("adsfasdf");
    }

[important parts of Class 2 ("Easy")]

public void e(){
        System.out.println("called class easy");

    int max = MainActivity.max;
    System.out.println(max);
    for (int i= 0; i<max; i++){
        System.out.println("runde"+i);
 MainActivity.Tx(i);

    }

I know, some people already asked such questions but I didn't find a working solution. I already understood, that you can't access the UI things outside the UI thread and that the nullpointerexception appears, because he uses the "empty" public static TextView A; and not the final TextView A = (TextView) findViewById(R.id.A).

But how I can make it visible for the other methods?

Sorry if the post looks messed up but I didn't konw how to explain my situation in a better way

eweb · Accepted Answer · 2013-05-08 13:15:33Z

1

Rather than defining a new local variable A, just assign to the static.

change

final    TextView A = (TextView) findViewById(R.id.A); //the textview I wanna chage

to

A = (TextView) findViewById(R.id.A); //the textview I wanna chage

answered May 8, 2013 at 13:15

eweb

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4 Comments

user2330482 Over a year ago

Thanks a lot for your answer, but unfortunately that didn't solve anything, I get exactly the same error like before :/

eweb Over a year ago

Have you verified that the call to findViewById is not returning null?

user2330482 Over a year ago

I already mentioned that, the findviewbyid is not read by Tx(). Tx() uses the public TextView A;thats the problem

eweb Over a year ago

I realise that. You have a class variable and a local variable both called A. You assign to the local, so of course the class varibale is still null. When you assignd to the class variable it was still null, so possibly the call to findViewById is returning null. You should try to avoid statics, perhaps you could pass a pointer to the class 1 instance to Easy.e

Dimanoid · Accepted Answer · 2013-05-08 13:17:16Z

0

remove static from both A and Tx (of course your MainActivity must be created by the time you call easy.e())

answered May 8, 2013 at 13:17

Dimanoid

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3 Comments

user2330482 Over a year ago

So I did, "Cannot make a static reference to the non-static method Tx(int) from the type MainActivity" .. What do you mean with MainActivity must be created the time I call easy.e() ?

Dimanoid Over a year ago

call it this way MainActivity.this.Tx(i);

user2330482 Over a year ago

Sorry for wasting your time, but now I got "No enclosing instance of the type MainActivity is accessible in scope" on that method. Just tried it with making an object of MainActivity, but that results in the same

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