Quiz project with XML and Java

Question

I'm learning to code Android apps and have recently finished a quiz app. I would like some feedback about best practices and possible ways to improve performance, as I'm also new to Java.

activity_main.xml:

<?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"
 android:fillViewport="true"
 tools:context="com.example.android.mathquiz.MainActivity"
 android:background="#C5CAE9">
 <LinearLayout
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:focusable="true"
 android:focusableInTouchMode="true"
 android:gravity="center_horizontal"
 android:orientation="vertical"
 android:paddingBottom="16dp"
 android:paddingLeft="16dp"
 android:paddingRight="16dp">
 <TextView
 style="@style/AllElements"
 android:text="Respondé las siguientes preguntas:" />
 <!-- QUESTION 1 [DONE]-->
 <TextView
 style="@style/Questions"
 android:text="1) La pendiente de una recta es su inclinación." />
 <RadioGroup
 style="@style/AllElements"
 android:id="@+id/question_one_answers"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content">
 <RadioButton
 android:id="@+id/question_one_answer_one"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Verdadero"/>
 <RadioButton
 android:id="@+id/question_one_answer_two"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Falso"/>
 </RadioGroup>
 <!-- QUESTION 2 [LISTO]-->
 <TextView
 style="@style/Questions"
 android:text="2) Indicar la ordenada al origen de la función:\ny = x" />
 <EditText
 style="@style/AllElements"
 android:id="@+id/question_two_answer"
 android:layout_width="match_parent"
 android:inputType="number"
 android:hint="Respuesta"/>
 <!-- QUESTION 3 [LISTO]-->
 <TextView
 style="@style/Questions"
 android:text="3) Indicar la pendiente de la función:\ny = x + 1" />
 <EditText
 style="@style/AllElements"
 android:id="@+id/question_three_answer"
 android:layout_width="match_parent"
 android:inputType="number"
 android:hint="Respuesta"/>
 <!-- QUESTION 4 -->
 <TextView
 style="@style/Questions"
 android:layout_marginBottom="0dp"
 android:text="4) ¿Cuáles son los requisitos de las funciones?" />
 <TextView
 style="@style/AllElements"
 android:layout_marginBottom="32dp"
 android:text="Seleccionar todas las opciones posibles." />
 <CheckBox
 android:id="@+id/question_four_answer_one"
 style="@style/AllElements"
 android:text="Unicidad" />
 <CheckBox
 android:id="@+id/question_four_answer_two"
 style="@style/AllElements"
 android:text="Positividad" />
 <CheckBox
 android:id="@+id/question_four_answer_three"
 style="@style/AllElements"
 android:text="Existencia" />
 <!-- CHECK ANSWERS -->
 <Button
 style="@style/AllElements"
 android:text="Revisar"
 android:layout_marginBottom="8dp"
 android:layout_marginTop="36dp"
 android:onClick="checkAnswers"/>
</LinearLayout>
</ScrollView>

MainActivity.java:

public class MainActivity extends AppCompatActivity {
 String[] correctAnswers = {"Falso", "0", "1", "Unicidad Existencia"};
 RadioGroup questionOneAnswers;
 RadioButton questionOneAnswerOne;
 RadioButton questionOneAnswerTwo;
 EditText questionTwoAnswer;
 EditText questionThreeAnswer;
 CheckBox questionFourAnswerOne;
 CheckBox questionFourAnswerTwo;
 CheckBox questionFourAnswerThree;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 // QUESTION 1
 questionOneAnswerOne = (RadioButton) findViewById(R.id.question_one_answer_one);
 questionOneAnswerTwo = (RadioButton) findViewById(R.id.question_one_answer_two);
 // QUESTION 2
 questionTwoAnswer = (EditText) findViewById(R.id.question_two_answer);
 // QUESTION 3
 questionThreeAnswer = (EditText) findViewById(R.id.question_three_answer);
 // QUESTION 4
 questionFourAnswerOne = (CheckBox) findViewById(R.id.question_four_answer_one);
 questionFourAnswerTwo = (CheckBox) findViewById(R.id.question_four_answer_two);
 questionFourAnswerThree = (CheckBox) findViewById(R.id.question_four_answer_three);
 questionOneAnswers = (RadioGroup) findViewById(R.id.question_one_answers);
 }
 private boolean isEmpty(EditText myeditText) {
 return myeditText.getText().toString().trim().length() == 0;
 }
 private String questionOneGetAnswer() {
 if (questionOneAnswerOne.isChecked()) {
 return questionOneAnswerOne.getText().toString();
 }
 else if (questionOneAnswerTwo.isChecked()) {
 return questionOneAnswerTwo.getText().toString();
 }
 else {
 return "";
 }
 }
 private String questionTwoGetAnswer() {
 if (!isEmpty(questionTwoAnswer)) {
 return questionTwoAnswer.getText().toString();
 }
 else {
 return "";
 }
 }
 private String questionThreeGetAnswer() {
 if (!isEmpty(questionThreeAnswer)) {
 return questionThreeAnswer.getText().toString();
 }
 else {
 return "";
 }
 }
 private String questionFourGetAnswer () {
 String returnString = "";
 if (questionFourAnswerOne.isChecked()) {
 returnString += questionFourAnswerOne.getText();
 }
 if (questionFourAnswerTwo.isChecked()) {
 returnString += " " + questionFourAnswerTwo.getText();
 }
 if (questionFourAnswerThree.isChecked()) {
 returnString += " " + questionFourAnswerThree.getText();
 }
 return returnString;
 }
 public void checkAnswers(View view) {
 String[] givenAnswers = {questionOneGetAnswer(), questionTwoGetAnswer(), questionThreeGetAnswer(), questionFourGetAnswer()};
 int right = 0;
 int wrong = 0;
 for (int i = 0; i < givenAnswers.length; i++) {
 if (givenAnswers[i].equals(correctAnswers[i])) {
 right++;
 }
 else {
 wrong++;
 }
 }
 String message;
 if (wrong == 0) {
 message = "You got all the questions right!";
 }
 else {
 message = "Respuestas correctas: " + right + "\nRespuestas incorrectas: " + wrong + "\n¡Inténtalo de nuevo!";
 }
 //Reset answer fields
 // QUESTION 1
 questionOneAnswers.clearCheck();
 // QUESTION 2
 questionTwoAnswer.setText("");
 // QUESTION 3
 questionThreeAnswer.setText("");
 // QUESTION 4
 questionFourAnswerOne.setChecked(false);
 questionFourAnswerTwo.setChecked(false);
 questionFourAnswerThree.setChecked(false);
 // Print out message with quiz results
 Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
 }
}

styles.xml:

<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
 <!-- Customize your theme here. -->
 <item name="colorPrimary">@color/colorPrimary</item>
 <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
 <item name="colorAccent">@color/colorAccent</item>
 <item name="android:textColor">@color/colorAccent</item>
</style>
<style name="AllElements">
 <item name="android:layout_width">wrap_content</item>
 <item name="android:layout_height">wrap_content</item>
 <item name="android:layout_marginTop">16dp</item>
 <item name="android:textSize">18sp</item>
 <item name="android:textAlignment">center</item>
 <item name="android:textColor">#0D47A1</item>
</style>
<style name="Questions" parent="AllElements">
 <item name="android:layout_marginBottom">16dp</item>
 <item name="android:layout_marginTop">32dp</item>
 <item name="android:textSize">26sp</item>
</style>
</resources>

Answer 1

1) You can remove the below function and directly use TextUtils.isEmpty

2) questionThreeGetAnswer() & questionTwoGetAnswer() can be refactor

 private String questionThreeGetAnswer() {
 return questionThreeAnswer.getText().toString();
 }

as questionThreeAnswer.getText().toString() always return "", if there is no data. So need to check for empty & return "".

Note:

In your case, if-else statement is useful only if you have to show an error for an empty answer.

• N J: Welcome :) glad to help you