To calculate difference between two times in android studio

Question

1. I created buttons for display current time for start and stop parking and its work.

2. But when I clicked on the deductbtn, the apps on the phone will pop up and show "my Application 1 has stopped"

3. How can I fix this? Any help will be much appciated.

   @Override
   protected void onCreate(final Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_payment_info);
   
   firebaseAuth = FirebaseAuth.getInstance();
   parkBtn = (Button)findViewById(R.id.parkBtn);
   stopparkBtn = (Button)findViewById(R.id.stopparkBtn);
   deductBtn = (Button)findViewById(R.id.deductBtn);
   timeResult = (TextView)findViewById(R.id.timeResult);
   timeResult2 = (TextView)findViewById(R.id.timeResult2);
   diffResult = (TextView)findViewById(R.id.diffResult);
   
   
   parkBtn.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
           final Date d = new Date();
           SimpleDateFormat sdf1=new SimpleDateFormat("hh:mm a");
           final String currentDateTimeString = sdf1.format(d);
           timeResult.setText(currentDateTimeString);
   
       }
   });
   
   stopparkBtn.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
           final Date d1= new Date();
           SimpleDateFormat sdf2 = new SimpleDateFormat("hh:mm a");
           final String currentDateTimeString1 = sdf2.format(d1);
           timeResult2.setText(currentDateTimeString1);
   
   
       }
   });
   
   deductBtn.setOnClickListener(new View.OnClickListener() {
   
       @Override
       public void onClick(View view) {
   
           float totalTime = Float.parseFloat(timeResult2.getText().toString());
           float totalTime1 = Float.parseFloat(timeResult.getText().toString());
           final float timeUsage = totalTime - totalTime1;
           diffResult.setText(String.valueOf(timeUsage));
   
       }
   });
   
   }
   
   }
   

Answer 1

The new code is here : @Override public void onClick(View view) {

            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm a");
            Date date1 = null;
            try {
                date1 = simpleDateFormat.parse(timeResult.getText().toString());
            } catch (ParseException e) {
                e.printStackTrace();
            }
            Date date2 = null;
            try {
                date2 = simpleDateFormat.parse(timeResult2.getText().toString());
            } catch (ParseException e) {
                e.printStackTrace();
            }
            String diffResult= DateUtils.getRelativeTimeSpanString(date1.getTime(), date2.getTime(), DateUtils.FORMAT_SHOW_TIME).toString();
            deductBtn.setText(diffResult);
        }

Answer 2

You are getting exception because

float totalTime = Float.parseFloat(timeResult2.getText().toString());
float totalTime1 = Float.parseFloat(timeResult.getText().toString());

Here, If you click this button after performing click on other buttons, then textview's text will be in the format hh:mm a

And if you click button for the first time without clicking other buttons , The strings will be empty

Both will throw exception

java.lang.NumberFormatException: Invalid float

You can use,

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm a");
date1 = simpleDateFormat.parse(timeResult2.getText().toString());
date2 = simpleDateFormat.parse(timeResult.getText().toString());
String diff= DateUtils.getRelativeTimeSpanString(date1.getTime(), date2.getTime(), DateUtils.HOUR_IN_MILLIS).toString();

Make sure that your textviews strings are not empty before doing it.