Android Studio : Simple input textbox and intercept key example

A GUI(Graphical User Interface) such as Android OS has input text box to allow users to enter text and able to capture the input for further processing. For this tutorial, we will learn how to create an editable text box widget in Android Studio and create a listener to process the input text string. We will also learn how to add a function to intercept certain key stroke entered by the user. For this example, we will intercept the space key.

Below is an image of the finished application:

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First, fill up the layout designer in Android Studio with the following code and save in the activity_main.xml file:

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 <?xml version="1.0" encoding="utf-8"?>
 <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="com.example.sweetlogic.inputtextbox.MainActivity">

 <EditText
 android:id="@+id/editTextInput"
 android:layout_width="368dp"
 android:layout_height="48dp"
 android:text="Color"
 android:inputType="textPersonName"
 android:visibility="visible"
 app:layout_constraintBottom_toBottomOf="parent"
 app:layout_constraintLeft_toLeftOf="parent"
 app:layout_constraintRight_toRightOf="parent"
 app:layout_constraintTop_toTopOf="parent"
 app:layout_constraintVertical_bias="0.107" />



 <Button
 android:id="@+id/buttonGetEditTextInput"
 android:layout_width="368dp"
 android:layout_height="48dp"
 android:text="Process input"
 app:layout_constraintBottom_toBottomOf="parent"
 app:layout_constraintLeft_toLeftOf="parent"
 app:layout_constraintRight_toRightOf="parent"
 app:layout_constraintTop_toTopOf="parent"
 tools:layout_editor_absoluteX="8dp"
 tools:layout_editor_absoluteY="231dp" />

 <TextView
 android:id="@+id/textView"
 android:layout_width="368dp"
 android:layout_height="48dp"
 android:text="What is your favorite color?"
 android:textColor="@android:color/background_dark"
 android:textSize="24sp"
 android:textStyle="bold"
 app:layout_constraintBottom_toBottomOf="parent"
 app:layout_constraintLeft_toLeftOf="parent"
 app:layout_constraintRight_toRightOf="parent"
 app:layout_constraintTop_toTopOf="parent"
 app:layout_constraintVertical_bias="0.004" />


 </android.support.constraint.ConstraintLayout>

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and fill in the Java codes at MainActivity.java with:

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 package com.example.sweetlogic.inputtextbox;

 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.widget.EditText;
 import android.widget.Button;
 import android.widget.Toast;
 import android.view.View;
 import android.view.KeyEvent;

 public class MainActivity extends AppCompatActivity {

 private EditText editTextInput;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);


 addButtonListener();

 }


 // intercept user input if space button is pressed
 public void interceptSpaceKey() {

 editTextInput = (EditText) findViewById(R.id.editTextInput);
 editTextInput.setOnKeyListener(new View.OnKeyListener() {

 public boolean onKey(View v, int keyCode, KeyEvent event) {

 // if the user press space button, display a toast message
 if ((keyCode == KeyEvent.KEYCODE_SPACE)) {

 // display a floating message
 Toast.makeText(MainActivity.this, "Cannot have space in input text!", Toast.LENGTH_LONG).show();
 return true;
 }
 return false;
 }

 });

 }

 public void addButtonListener() {
 Button button = (Button) findViewById(R.id.buttonGetEditTextInput);
 editTextInput = (EditText) findViewById(R.id.editTextInput);

 // check for space key
 interceptSpaceKey();

 button.setOnClickListener(new View.OnClickListener() {

 @Override
 public void onClick(View arg0) {


 Toast.makeText(MainActivity.this, editTextInput.getText(), Toast.LENGTH_LONG).show();
 }

 });
 }


 }

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Save all the files and hit the Run button and you should be able to see the application running on your selected Android Virtual Device.

Here is an image of the application processing user input:

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and intercept the space key:

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Hope you find this tutorial useful for learning Android Studio and happy coding!