Android Change TextView text from another class

Question

I have a TextView in MainActivity, I would like to change the TextView text within another class.

How can I access TextView in MainActivity from another class?

I tried the following

TextView textView = (TextView) findViewById(R.id.myTextView);

textView.setText("Text");

But the app crashes when calling setText()

Answer 1

You have to use runOnUiThread(new Runnable()...

See following:

import android.content.Context;

private class AnotherClass {
        protected MainActivity context;

        public AnotherClass(Context context){
            this.context = (MainActivity) context;
        }

        public void updateTV(final String str1){
            context.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    context.textView.setText(str1);    
                }
            });
        }
    }

Answer 2

If you want to update the text of the TextView a possible way would be to edit the text in a common data model that is shared by your classes. If onResume from the activity is called later it can read the new value from the model and update the TextView.