Madona Syombua
Passionate Android Developer
Ever thought of solving an algorithm question on Android Studio?
@madona_syombua x @wwcodemobile
Step 1. Download and Install Android Studio
Step 2: Let's create our first project
Step 3: Start a new project, let's use the default empty activity screen.
Step 4: Creating our first App. Language of use Java.
Once everything is set up and ready, we will go ahead and work on the following question.
Quiz 1.
Given a String "Hello" - Reverse it. So output should be "olleH"
So to briefly describe the process.
We will need the following Android Views.
- EditText - where we will enter the string to be reversed.
- Button - which will have the method "reverseString();" that is the operation
- TextView - Which will display the reversed String, that is our output.
- Button clear which will clear the Edittext and Textview space
Let's go ahead and add some dependencies. Butter Knife Field and method binding for Android views
//jake wharton
implementation 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'Display Screen - Activity_Main.Xml
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<!-- edit text used to reverse String-->
<EditText
android:id="@+id/reverse_edit_text"
android:layout_width="306dp"
android:layout_height="47dp"
android:layout_marginStart="16dp"
android:layout_marginTop="32dp"
android:ems="10"
android:fontFamily="monospace"
android:hint="@string/enter_string"
android:inputType="textPersonName"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/textView"
tools:targetApi="o" />
<!-- submit button -->
<Button
android:id="@+id/reverse"
android:layout_width="147dp"
android:layout_height="48dp"
android:layout_marginStart="16dp"
android:layout_marginTop="36dp"
android:background="@color/colorPrimary"
android:fontFamily="monospace"
android:text="@string/button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/reverse_edit_text" />
<!-- reverse text view -->
<TextView
android:id="@+id/reverse_textView"
android:layout_width="209dp"
android:layout_height="30dp"
android:layout_marginStart="16dp"
android:layout_marginTop="40dp"
android:fontFamily="monospace"
android:textSize="16sp"
android:textColor="@color/colorAccent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/reverse" />
<!-- Clear button -->
<Button
android:id="@+id/clear"
android:layout_width="144dp"
android:layout_height="41dp"
android:layout_marginStart="16dp"
android:layout_marginTop="40dp"
android:background="@color/colorPrimary"
android:fontFamily="monospace"
android:text="@string/clear_button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/reverse_textView" />
<!-- Intro Text View-->
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="36dp"
android:fontFamily="monospace"
android:text="@string/intro"
android:textColor="@color/colorAccent"
android:textSize="16sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>Preview
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import butterknife.BindView;
import butterknife.ButterKnife;
public class MainActivity extends AppCompatActivity {
@BindView(R.id.reverse_edit_text)
EditText reverseEdittext;
@BindView(R.id.reverse)
Button buttonReverse;
@BindView(R.id.reverse_textView)
TextView reverseTextView;
@BindView(R.id.clear)
Button clearButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
buttonReverse.setOnClickListener(view -> ReverseString());
//clearing the textView and EditText
clearButton.setOnClickListener(view -> {
reverseEdittext.getText().clear();
reverseTextView.setText(" ");
});
}
static String reverseString(myString string, String str){
return string.myStringFunction(str);
}
//Reverse string
private void ReverseString(){
myString reverse = (String str)->{
int n = str.length() - 1;
StringBuilder results = new StringBuilder();
for(int i = n; i >= 0; i--){
results.append(str.charAt(i));
}
return results.toString();
};
//appending the reversed String to the text view;
reverseTextView.append(reverseString(reverse, String.valueOf(reverseEdittext.getText())));
}
interface myString{
String myStringFunction(String str);
}
}
Part One : Code Snippet - posted on GitHub https://github.com/WomenWhoCode/WWCodeMobile-solving-Java-algorithms
Using BindView to fetch the views on our XML code
buttonReverse.setOnClickListener(view -> ReverseString());
//clearing the textView and EditText
clearButton.setOnClickListener(view -> {
reverseEdittext.getText().clear();
reverseTextView.setText(" ");
});we set on click listener to the buttonReverse and start the method ReverseString which reverses the entered text on the EditText.
We set on click listener to the clearButton to clear the EditText space and TextView space.
Lambda expressions are added in Java 8 and help make the code more Concise and readable.
we use our interface to store the string to be reversed then loop through the length of the string -1 , using the StringBuilder we append the characters that were reversed then later append it on the reverseTextView after we return the results to string.
static String reverseString(myString string, String str){
return string.myStringFunction(str);
}
//Reverse string
private void ReverseString(){
myString reverse = (String str)->{
int n = str.length() - 1;
StringBuilder results = new StringBuilder();
for(int i = n; i >= 0; i--){
results.append(str.charAt(i));
}
return results.toString();
};
//appending the reversed String to the text view;
reverseTextView.append(reverseString(reverse, String.valueOf(reverseEdittext.getText())));
}Solution:
Thank you very much for your time, all materials will be shared on Women Who Code GitHub page.
https://github.com/WomenWhoCode/WWCodeMobile-solving-Java-algorithms
Find US
Twitter : @WWCodeMobile , @madona_syombua
Instagram : @wwcodemobile , @madona_syombua
Solving an Algorithm question on Android Studio. Women Who Code Mobile Webinar
By Madona Syombua
Solving an Algorithm question on Android Studio. Women Who Code Mobile Webinar
Taking an algorithm question and solving it on Android Studio, that is creating an app with the solution to the question. Educator: Madona Syombua | Android Engineer, Founder of Budgeting Buddy, Grow with Google Recipient, WWCode Mobile Android Lead Twitter: @madona_syombua GitHub: @madonahs
