simple math with users input

Question

I am new in java and Android. I am working on simple project that's almost complete. But I am facing some problem in XML layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <EditText
        android:id="@+id/a"
        android:layout_width="35dp"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:inputType="number"
        android:minWidth="60dp" />

    <Button
        android:id="@+id/button1"
        android:layout_width="47dp"
        android:layout_height="wrap_content"
        android:text="Button" />

    <TextView 
        android:id="@+id/total"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp" />

</LinearLayout>

When a user enters a number in edit text and press the button then text view should show this result:

"enters number minus(-)30"

Like if a user enter number 50 then result show 20 in the text box (50-30=20)

I know only basic Java and I never do math in Java before so I dont know what i write in code. Search a lot on google and stackoverflow.com and also read many books but never find that simple math.

Any help would be appreciated.

Sagar Maiyad · Accepted Answer · 2013-06-10 06:51:45Z

2

btnsub.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                String edtval = edttxt.getText().toString().trim();

                           if(!edtval.equals("")){
                               int val = Integer.parseInt(edtval);
                               int finalval = val - 30;

                              textview.setText(finalval+"");
                         }
            }
        });

edited Jun 10, 2013 at 6:51

answered Jun 10, 2013 at 6:44

Sagar Maiyad

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1 Comment

Mohammed Azharuddin Shaikh Over a year ago

textview.setText(val - 30); will throw error i.e. String Resource not found

Venkatesh S · Accepted Answer · 2013-06-10 07:22:46Z

1

btnsub.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            String edtval = edttxt.getText().toString().trim();

                       if(!edtval.equals("")){
                           int val = Integer.parseInt(edtval);
                           int finalval = val - 30;

                          textview.setText(String.valueOf(finalval));
                     }
        }
    });

answered Jun 10, 2013 at 7:22

Venkatesh S

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Comments

DevZer0 · Accepted Answer · 2013-06-10 06:55:25Z

Simple math is very simple to perform.

You first need to get a references to your Views as follows

EditText editText = (EditText) findViewById(R.id.a);

Button button = (Button) findViewById(R.id.button1);

TextView textView = (TextView) findViewById(R.id.total);

Then set an onClickListener for the Button and do the operation inside the onClick Method

button.setOnClickListener(new OnClickListener() {

     @Override
     public void onClick(View v) {
          Integer input = 0;
          try {
              input = Integer.parseInt(editText.getText().toString());
          } catch (NumberFormatException e) {
              input = 0;
          } 
          input = input - 30;
          textView.setText(input.toString() + "");
     }
}

Parijat Bose · Accepted Answer · 2013-06-10 06:54:39Z

-1

btnsub.setOnClickListener(new OnClickListener() {

        @Override
            public void onClick(View v) {
  int num;
        try {
              num= Integer.parseInt(edttxt.getText().toString());
              textview.setText(""+(num - 30));
         } catch (NumberFormatException e) {
             // Open a dialog for incorrect input,i.e., Not a number
         }

        }
    });

edited Jun 10, 2013 at 6:54

answered Jun 10, 2013 at 6:47

Parijat Bose

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5 Comments

Mohammed Azharuddin Shaikh Over a year ago

what about "Blank" space checking?. An EditText may contain white space.

Parijat Bose Over a year ago

The edittext may contain string values also, chk my code for this exception, which includes your space thing also!

Mohammed Azharuddin Shaikh Over a year ago

This is not the correct way, you can use trim() to overcome the same.

Parijat Bose Over a year ago

You are telling half of the story. What about if any user inputs some string eg. "50 s" ?

Mohammed Azharuddin Shaikh Over a year ago

EditText having property of InputType, so one can bound user to input numbers only.

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