Thread: Optimize code Java in activity and long operation

hello I have a problem with java and android develop a dual timer with the Runnable class.
By means of a call first the activity mRunnable and then the mRunnable1 at a distance of a few seconds. The problem is that when viewing the screen "DownTot.setText (a);" show me for a moment and then subsequently rxbytes the difference (rxbytes - rxbytes1). This is done as if the operation was slow. is there a way to optimize my code?
Here is the code below:

public class MainActivity extends Activity implements OnClickListener  {
 
    TextView DownTot;
    private long rxBytes;
    private long rxBytes1;
private final Runnable mRunnable = new Runnable() {
    	public void run() {
        mHandler.postDelayed(mRunnable1, 1000);
        TextView DownTot = (TextView)findViewById(R.id.downtot);
        rxBytes = (TrafficStats.getTotalRxBytes()- StartDown);
    	long a = rxBytes - rxBytes1;
    	DownTot.setText(a);
    	}
    };
 
    private final Runnable mRunnable1 = new Runnable() {
    	public void run() {
        mHandler.postDelayed(mRunnable1, 1000);
        TextView DownTot = (TextView)findViewById(R.id.downtot);
        rxBytes1 = (TrafficStats.getTotalRxBytes()- StartDown);
    	long a = rxBytes1 - rxBytes;
    	DownTot.setText(a);
    	}
    };
 
......

I do not understand what the code is supposed to do. Post enough code to see the plan and try to explain what it should do, or what you want it to do.