Android Text vanishes from text view after next input

Question

I am new to the android studio and I was building a calculator app, my problem is whenever I enter a number and then select an operator the number from the text view vanishes like if I want 2+4 and I press 2 and then +, 2 vanishes from the text view and then when I press 4, + vanishes from the text view but the result is correct

Here is my java code...

    buttonAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if (edt1 == null){
                edt1.setText("");
            }else {
                mValueOne = Float.parseFloat(edt1.getText() + "");
                mAddition = true;
                edt1.setText(null);
            }
        }
    });

    buttonSub.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mValueOne = Float.parseFloat(edt1.getText() + "");
            mSubtract = true ;
            edt1.setText(null);
        }
    });

    buttonMul.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mValueOne = Float.parseFloat(edt1.getText() + "");
            mMultiplication = true ;
            edt1.setText(null);
        }
    });

    buttonDivision.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mValueOne = Float.parseFloat(edt1.getText()+"");
            mDivision = true ;
            edt1.setText(null);
        }
    });

    buttonEqual.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mValueTwo = Float.parseFloat(edt1.getText() + "");

            if (mAddition == true){

                edt1.setText(mValueOne + mValueTwo +"");
                mAddition=false;
            }


            if (mSubtract == true){
                edt1.setText(mValueOne - mValueTwo+"");
                mSubtract=false;
            }

            if (mMultiplication == true){
                edt1.setText(mValueOne * mValueTwo+"");
                mMultiplication=false;
            }

            if (mDivision == true){
                edt1.setText(mValueOne / mValueTwo+"");
                mDivision=false;
            }
        }
    });

    buttonC.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            edt1.setText("");
        }
    });

    button10.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            edt1.setText(edt1.getText()+".");
        }
    });
}

Answer 1

You are collecting the data correctly, but you keep setting your edt1 to null, and then when you hit + edt1 will always be null

 if (edt1 == null){
            edt1.setText("");
        }

May i ask why you are using the same editText field for doing this??

I would suggest using 2 edittext fields.

1 for first number 1 for second number

and then display the result in a textview?

You can achieve something like this with the code below

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="1">

    <EditText
        android:id="@+id/first_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2"
        android:layout_weight="0.40"/>

    <EditText
        android:id="@+id/second_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2"
        android:layout_weight="0.40"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=" = "
        android:layout_weight="0.10"/>

    <TextView
        android:id="@+id/result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="4"
        android:layout_weight="0.20"/>

</LinearLayout>

Then you can collect data from first_number and second_number and displaying the result in result.

Answer 2

use the append method to add text after existing

edt1.append(someString);

Answer 3

You are setting the Edit Text to null every time a button is clicked. This will clear al the text inside it. And if you want add text use the append method.