Android dev't using thread with textview: why this is crashing?

Question

My goal is when the user tap start button, letters "o" "n" "o" "m" and so forth will appear at the center of the screen. "o" will appear first then after a few seconds will be replaced by "n" then "o" and so forth.

note: for brevity, i just make the guessword = onomatopoeia, first. In reality, guessword will changes every time i tap the start bottom.

this is the code:

    private String guessword = "onomatopoeia";
private TextView showchar;
private int n = guessword.length();
private char letArray[]= guessword.toCharArray();;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_play); 

    addStartListener();

}

public void addStartListener(){
    Button start = (Button) findViewById(R.id.start);
    showchar = (TextView) findViewById (R.id.charView);

    start.setOnClickListener(new OnClickListener(){

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub

            Thread thread = new Thread()
            {
                @Override
                public void run() {
                    try {
                        for(int i = 0 ; i < n ; i++) {
                            sleep(1000);
                            showchar.setText(letArray[i]);
                        }
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            };

            thread.start();

        }



    });

}

thanks for the help

I decided to implement runonuithread but still it crashes:

this is the updated version:

private String guessword = "onomatopoeia";
private TextView showchar;
private int n = guessword.length();
private char letArray[]= guessword.toCharArray();
private Handler handler;
private int i = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_play); 
    handler = new Handler();
    showchar = (TextView) findViewById (R.id.charView);
}

public void startGame(View view){
    new Thread() {
        public void run() {
            while(i++ < n) {
                try {
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                             showchar.setText(letArray[i]);
                        }
                    });
                    Thread.sleep(300);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }.start();

}   

Answer 1

use this code for setting the text in your textview

               runOnUiThread(new Runnable() {

                    @Override
                    public void run() {
                       showchar.setText(letArray[i]);
                    }
                });

Answer 2

You are updating ui from a thread which is not possible.

showchar.setText(letArray[i]);

UI must be updated ui thread.

All you are doing is repeatedly setting value to TextView you can use Handler with a delay for this purpose.

You could use runOnUiThread also but i don't see the need for a thread for what you are doing.

Use a Handler. You can find an example @

Android Thread for a timer