how to refresh the screen content ?

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Java

Mobile

Android

I am trying to display a user's exercise data on a specific date from a sqlite database like this :

Exercises 252.5
walking,30min 70
Running,30min 125.4
treadmill.30min 57.1

in each time the user select a date i retrieve the information of all exercises that are stored in that date and display them in this format , but these information appear only when i remove the excercises_LL.removeAllViews() statement from my code ,and in this case as the user select a date the returned data displayed above the previous one , but i want to do this : in each time the user choose a date the screen content is refreshed so it contains only the data of all exercises returned in that date otherwise " if there is no data returned from the data base( cursor is null)" i want to change the back ground to an image says that there is no data has been inserted .

how i can refresh the content of screen ? and change the screen background?
please help me how i can do that?



this is my code

public class Tracker extends BaseActivity
{
    private Button date_btn;
    private ImageButton  left_btn;
    private ImageButton  right_btn;
    private ImageView    nodata;
    private TextView ex_name;
    private TextView ex_BCals;
    
    private LinearLayout  excercises_LL;
    private  LinearLayout content_LL ;
    private LinearLayout  notes;
    
    private int year,month,day;
    private double  tot_excals_burned;
    private Calendar  localCalendar; 
    private static final int DATE_DIALOG_ID=0;

    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.tracker);
    
    
    
        date_btn=(Button)findViewById(R.id.btn_date);
        date_btn.setText(FormatDate());
        date_btn.setOnClickListener(new View.OnClickListener() {
    
            public void onClick(View v) {
                localCalendar = Calendar.getInstance(); 
                year = localCalendar.get(1);
                month= localCalendar.get(2);
                day  =  localCalendar.get(5);
                showDialog(DATE_DIALOG_ID);
            }
    });


    left_btn=(ImageButton)findViewById(R.id.btn_left);
    left_btn.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            localCalendar.add(5, -1);
            date_btn.setText(FormatDate(localCalendar,"EEEE, d/MMM/yyyy"));
            RefreshExercisesData();

        }
    });

    right_btn=(ImageButton)findViewById(R.id.btn_right) ;
    right_btn.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            localCalendar.add(5, 1);
            date_btn.setText(FormatDate(localCalendar,"EEEE, d/MMM/yyyy"));
            RefreshExercisesData();
        }
    });


    RefreshExercisesData();
}

private String  FormatDate()
{   

    localCalendar = Calendar.getInstance();
    return new  SimpleDateFormat("EEEE, d/MMM/yyyy").format(localCalendar.getTime());

}

private String FormatDate(int year, int month, int day)
{   
    localCalendar = Calendar.getInstance();
    localCalendar.set(year, month, day);

    return new  SimpleDateFormat("EEEE, d/MMM/yyyy").format(localCalendar.getTime());
}

private String FormatDate(Calendar   calendar , String  format)
{

    return new  SimpleDateFormat(format).format(calendar.getTime());

}






private void RefreshExercisesData()
{   
    nodata=(ImageView)findViewById(R.id.no_data_image);

    excercises_LL=(LinearLayout)findViewById(R.id.ll_exercises);
    tot_excals_burned=0;

    DBAdapter db = new DBAdapter(this);
    db.open();
    String selected_date= date_btn.getText().toString();
    Log.e("date", selected_date);


    Cursor c = db.getExerciseInfo(selected_date);

    if(c !=null)
    {

        nodata.setVisibility(8);
        excercises_LL.removeAllViews();
        excercises_LL.setWeightSum(1.0F);
        excercises_LL.setVisibility(0);
        excercises_LL.setOrientation(LinearLayout.VERTICAL);

        LayoutInflater exc_LayoutInflater = (LayoutInflater)getApplicationContext().getSystemService("layout_inflater");


        LinearLayout layout = (LinearLayout)exc_LayoutInflater.inflate(R.layout.tracker_header_item,null);
        TextView   tot_ex_cals_value=((TextView)(layout).findViewById(R.id.tv_tot_cals_value));
        TextView   exs_title=((TextView)(layout).findViewById(R.id.tv_item_title)) ;
        exs_title.setText("Exercises ");

        (layout).setPadding(0, 36, 0, 0);
        excercises_LL.addView((View)layout, 0);
        int i = 1;

        if (c.moveToFirst())
        {
            do 
            {
                content_LL=new LinearLayout(this);

                ex_name=new TextView(this);
                ex_name.setText( " "+c.getFloat(1)+", " +c.getString(0) + " minute");
                ex_name.setTextColor(R.color.black);
                content_LL.addView(ex_name,0);
                ex_BCals=new TextView(this);
                ex_BCals.setText(Round(c.getFloat(2)) +" ");
                ex_BCals.setTextColor(R.color.black);
                tot_excals_burned = tot_excals_burned+c.getFloat(2);

                content_LL.addView(ex_BCals,1);
                excercises_LL.addView(content_LL, i);


                i++; 

            }
            while (c.moveToNext());

        }
        tot_ex_cals_value.setText(Round(tot_excals_burned) + " cals");

    }
    else
    {    
        nodata.setVisibility(0);
    }
    c.close();
    c.deactivate();
    db.close();

}



protected Dialog onCreateDialog(int id)
{
    switch (id) {

    case DATE_DIALOG_ID:
        return new DatePickerDialog(this, mDateSetListener, this.year, this.month, this.day);
    }
    return null;
}

private DatePickerDialog.OnDateSetListener mDateSetListener = new DatePickerDialog.OnDateSetListener()
{
    public void onDateSet(DatePicker paramDatePicker, int year, int monthofYear, int dayofMonth)
    {
        Tracker.this.year=year;
        month=monthofYear;
        day=dayofMonth;
        date_btn.setText(FormatDate(year,month,day));
        RefreshExercisesData();

    }

};


private  String Round(double num) {
    return String.format("%.1f%n", num);

}}