Question

I have this code

package com.lestijden;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

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

    Datum = (TextView) findViewById(R.id.Tijd);

    Date today = Calendar.getInstance().getTime();
    SimpleDateFormat Formatter = new SimpleDateFormat("km");
    String folderName = Formatter.format(today);

    int result = folderName.compareTo("0");


    if (result > 815 ){
        double data = new Double("905") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 905){
        double data = new Double("955") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }

    else if (result > 955){
        double data = new Double("1045") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }

    else if (result > 1045){
        double data = new Double("1100") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }

    else if (result > 1100){
        double data = new Double("1150") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1150){
        double data = new Double("1240") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1240){
        double data = new Double("1310") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1310){
        double data = new Double("1400") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1400){
        double data = new Double("1450") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1450){
        double data = new Double("1505") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1505){
        double data = new Double("1555") - new Double(folderName); 
        Datum.setText(Double.toString(data));
    }
    else if (result > 1555){
        double data = new Double("1645") - new Double(folderName); 
        Datum.setText(Double.toString(data));

    }
}
}

I want it to work like this: if the time is for example 14:01. (1401) then it needs to make a calculation 1450 minus the current time (1401). and display the output (49) in a textview.

My textview does not display any output. how do i solve this?

Answer 1

You should convert the Strings to time objects. Substract these two times and convert the result to a String.

java.text.DateFormat df = new java.text.SimpleDateFormat("hh:mm");
java.util.Date date1 = df.parse("14:01");
java.util.Date date2 = df.parse("14:50");
long diff = date2.getTime() - date1.getTime();

Diff will be the time difference in milliseconds.