I have an activity with two play and pause buttons (currently invisible) and a seekbar. When I press the play button, the pause button should become visible, and when I press the pause button it should turn invisible.

How would I do that?

```
import android.media.MediaPlayer;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

    public class MainActivity extends Activity implements Runnable, OnClickListener, OnSeekBarChangeListener{
        private SeekBar seekBar;
        private Button startMedia;
        private Button pauseMedia;
        private MediaPlayer mp;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);             

            AudioControl();         

        }

        public void AudioControl(){
            seekBar = (SeekBar) findViewById(R.id.seekBar1);
            startMedia = (Button) findViewById(R.id.button1);
            pauseMedia = (Button) findViewById(R.id.button2);
            seekBar.setOnSeekBarChangeListener(this);
            startMedia.setOnClickListener(this);
            pauseMedia.setOnClickListener(this); 
        }

        public void run() {
            int currentPosition= 0;
            int total = mp.getDuration();
            while (mp!=null && currentPosition<total) {
                try {
                    Thread.sleep(1000);
                    currentPosition= mp.getCurrentPosition();
                } catch (InterruptedException e) {
                    return;
                } catch (Exception e) {
                    return;
                }            
                seekBar.setProgress(currentPosition);
            }
        }

        public void onClick(View v) {
            if (v.equals(startMedia)) {
                if (mp != null && mp.isPlaying()) return;
                if(seekBar.getProgress() > 0) {
                    mp.start();
                    return;
                }
                mp = MediaPlayer.create(MainActivity.this, R.raw.lone);
                mp.start();                     
                seekBar.setProgress(0);
                seekBar.setMax(mp.getDuration());
                new Thread(this).start();
            }

            if (v.equals(pauseMedia) && mp!=null) {
                mp.pause();
            }       

        }

        public void onStartTrackingTouch(SeekBar seekBar) {
        }

        public void onStopTrackingTouch(SeekBar seekBar) {
        }

        public void onProgressChanged(SeekBar seekBar, int progress,
                boolean fromUser) {
            if(fromUser) mp.seekTo(progress);

        }
    }

```

**I don't know where should I put blow code. please help me!**