I am developing a BASIC CALCULATOR android application and I stuck at a certain stage. This application takes input from the textview and gets it stored in a number.
The problem occurs while taking second input from the user.
I am setting the string used to take the first input(first number) to be null. Using the same string, how can I make the string null and allow for the second input after the operation is defined. Anyone out there could help me and be grateful to me.
Thank You in advance..
public class MainActivity extends AppCompatActivity {
String answer = "";
float num1, num2;
int flag = 0;
String operation = "";
TextView textViewAnswer;
Button buttonOne;
Button buttonTwo;
Button buttonThree;
Button buttonFour;
Button buttonFive;
Button buttonSix;
Button buttonSeven;
Button buttonEight;
Button buttonNine;
Button buttonZero;
Button buttonAddition;
Button buttonSubstraction;
Button buttonMultiplication;
Button buttonDivision;
Button buttonDot;
Button buttonEqual;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textViewAnswer = (TextView) findViewById(R.id.textview_answer);
}
public void one(View view){
buttonOne = (Button) findViewById(R.id.button_one);
if (flag == 1) {
num1 = Float.parseFloat(textViewAnswer.getText().toString());
flag = 0;
answer = "";
}
else {
checkLength(buttonOne);
textViewAnswer.setText(answer);
}
}
public void two(View view){
buttonTwo = (Button) findViewById(R.id.button_two);
checkLength(buttonTwo);
textViewAnswer.setText(answer);
if (flag == 1) {
num1 = Float.parseFloat(textViewAnswer.getText().toString());
flag = 0;
answer = "";
}
}
public void three(View view){
buttonThree = (Button) findViewById(R.id.button_three);
checkLength(buttonThree);
textViewAnswer.setText(answer);
}
public void four(View view){
buttonFour = (Button) findViewById(R.id.button_four);
checkLength(buttonFour);
textViewAnswer.setText(answer);
}
public void five(View view){
buttonFive = (Button) findViewById(R.id.button_five);
checkLength(buttonFive);
textViewAnswer.setText(answer);
}
public void six(View view){
buttonSix = (Button) findViewById(R.id.button_six);
checkLength(buttonSix);
textViewAnswer.setText(answer);
}
public void seven(View view){
buttonSeven = (Button) findViewById(R.id.button_seven);
checkLength(buttonSeven);
textViewAnswer.setText(answer);
}
public void eight(View view){
buttonEight = (Button) findViewById(R.id.button_eight);
checkLength(buttonEight);
textViewAnswer.setText(answer);
}
public void nine(View view){
buttonNine = (Button) findViewById(R.id.button_nine);
checkLength(buttonNine);
textViewAnswer.setText(answer);
}
public void zero(View view){
buttonZero = (Button) findViewById(R.id.button_zero);
checkLength(buttonZero);
textViewAnswer.setText(answer);
}
public void dot(View view){
buttonDot = (Button) findViewById(R.id.button_dot);
checkLength(buttonDot);
textViewAnswer.setText(answer);
}
public void equal(View view){
buttonEqual = (Button) findViewById(R.id.button_equal);
// textViewAnswer.setText(buttonEqual.getText().toString());
switch (operation){
case "+" : num2 = num1 + (Float.parseFloat(textViewAnswer.getText().toString()));
answer = ( String.valueOf(num2) );
textViewAnswer.setText(answer);
}
}
public void addition(View view){
buttonAddition = (Button) findViewById(R.id.button_addition);
textViewAnswer.setText(buttonAddition.getText().toString());
operation = "+";
flag = 1;
}
public void substraction(View view){
buttonSubstraction = (Button) findViewById(R.id.button_substraction);
textViewAnswer.setText(buttonSubstraction.getText().toString());
operation = "-";
}
public void division(View view){
buttonDivision = (Button) findViewById(R.id.button_division);
textViewAnswer.setText(buttonDivision.getText().toString());
operation = "/";
}
public void multiplication(View view){
buttonMultiplication = (Button) findViewById(R.id.button_multiplication);
textViewAnswer.setText(buttonMultiplication.getText().toString());
operation = "*";
}
public void checkLength(Button button){
if((answer.length()) < 9)
answer += button.getText().toString();
else
Toast.makeText(this, "Cannot take more input", Toast.LENGTH_SHORT).show();
}
}
Layout:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.darpan.basiccalculator.MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_gravity="bottom">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Answer"
android:id="@+id/textview_answer"
android:textSize="50sp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/button_one"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="1"
android:onClick="one"/>
<Button
android:id="@+id/button_two"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="2"
android:onClick="two"/>
<Button
android:id="@+id/button_three"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="3"
android:onClick="three"/>
<Button
android:id="@+id/button_addition"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="+"
android:onClick="addition"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/button_four"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="4"
android:onClick="four"/>
<Button
android:id="@+id/button_five"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="5"
android:onClick="five"/>
<Button
android:id="@+id/button_six"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="6"
android:onClick="six"/>
<Button
android:id="@+id/button_substraction"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="-"
android:onClick="substraction"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/button_seven"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="7"
android:onClick="seven"/>
<Button
android:id="@+id/button_eight"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="8"
android:onClick="eight"/>
<Button
android:id="@+id/button_nine"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="9"
android:onClick="nine"/>
/>
<Button
android:id="@+id/button_multiplication"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="*"
android:onClick="multiplication"/>
/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/button_dot"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="."
android:onClick="dot"/>
<Button
android:id="@+id/button_zero"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="0"
android:onClick="zero"/>
<Button
android:id="@+id/button_equal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="="
android:onClick="equal"/>
<Button
android:id="@+id/button_division"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="/"
android:onClick="division"/>
</LinearLayout>
</LinearLayout>
</ScrollView>
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