Android view not showing up when I call it the 2nd time

Question

Recently I have taken a chatting project which uses Android to implement.

In the main page, it shows all the groups. Then if a user click a group, he will be brought into the group page. The chat history will be retrieved. I used a function "printLeftSide" to print all history records. For the first time, it works. But if I click back button and then re-enter the group page, the history records are not seen and disappears. I have traced the "printLeftSide" function and the data is right to add views to the linear layout. The "printLeftSide" function is shown in the following:

void printLeftSide(String s, String name, Date dt)
{
    Display display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    try {
        display.getRealSize(size);
    } catch (NoSuchMethodError err) {
        display.getSize(size);
    }
    int width = size.x;
    int height = size.y;

    LinearLayout llMessageDT = new LinearLayout(this);
    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
            2*width/5,
            LinearLayout.LayoutParams.WRAP_CONTENT);

    params.setMargins(10,10,10,10);

    llMessageDT.setOrientation(LinearLayout.HORIZONTAL);

    llMessageDT.setLayoutParams(params);

    DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String dt_ = (String) df.format(dt);

    TextView tv3 = new TextView(thisView);
    tv3.setTextSize(10);
    tv3.setText(dt_);
    tv3.setGravity(Gravity.LEFT);

    TextView tv = new TextView(thisView);
    tv.setTextSize(12);
    tv.setText(name+" - ");
    tv.setGravity(Gravity.LEFT);

    llMessageDT.addView(tv);
    llMessageDT.addView(tv3);

    TextView tv2 = new TextView(thisView);
    tv2.setTextSize(20);
    tv2.setText(s);
    tv2.setGravity(Gravity.LEFT);

    LinearLayout ll = (LinearLayout) findViewById(R.id.messageLinearLayout);
    ll.addView(llMessageDT, params);
    ll.addView(tv2, params);
}

I am quite confusing about the result. Is there anyone giving some hints to me to solve this problem? Thanks you very much for your attention.