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()+".");
        }
    });
}

```