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Example : An Android app for a simple calculator in a LinearLayout view.
strings.xml
<string-array name="Gen">
<item>Male</item>
<item>Female</item>
<item>Other</item>
</string-array>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical"
android:id="@+id/main"
tools:context=".MainActivity">
<EditText
android:id="@+id/editTextNumber1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter number 1" />
<EditText
android:id="@+id/editTextNumber2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter number 2" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/addButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:text="+" />
<Button
android:id="@+id/subButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="05dp"
android:textStyle="bold"
android:text="-" />
<Button
android:id="@+id/multButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="05dp"
android:textStyle="bold"
android:text="*" />
<Button
android:id="@+id/divButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:layout_marginLeft="05dp"
android:text="/" />
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/moddivButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="05dp"
android:textStyle="bold"
android:text="%" />
<Button
android:id="@+id/clearButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="05dp"
android:textStyle="bold"
android:text="Clear" />
</LinearLayout>
<TextView
android:id="@+id/resultTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
MainActivity.java
package com.example.myapplication2;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
public class MainActivity extends AppCompatActivity
{
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
EdgeToEdge.enable(this);
setContentView(R.layout.activity_main);
ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
return insets;
});
EditText editText1,editText2;
Button addButton1,subButton1, multButton1, divButton1, moddivButton1,clearButton;
TextView resultTextView;
editText1 = findViewById(R.id.editTextNumber1);
editText2 = findViewById(R.id.editTextNumber2);
addButton1 = findViewById(R.id.addButton);
subButton1 = findViewById(R.id.subButton);
multButton1 = findViewById(R.id.multButton);
divButton1 = findViewById(R.id.divButton);
moddivButton1 = findViewById(R.id.moddivButton);
clearButton=findViewById(R.id.clearButton);
resultTextView = findViewById(R.id.resultTextView);
editText1.requestFocus(); //Set cursor focus on Load event
editText1.requestFocusFromTouch(); //Set cursor focus on Load event
addButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int num1 = Integer.parseInt(editText1.getText().toString());
int num2 = Integer.parseInt(editText2.getText().toString());
int sum = num1 + num2;
resultTextView.setText("Sum of the value is : " + sum);
}
});
subButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int num1 = Integer.parseInt(editText1.getText().toString());
int num2 = Integer.parseInt(editText2.getText().toString());
int sub = num1 - num2;
resultTextView.setText("Subtraction of the value is : " + sub);
}
});
multButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int num1 = Integer.parseInt(editText1.getText().toString());
int num2 = Integer.parseInt(editText2.getText().toString());
int mult = num1 * num2;
resultTextView.setText("Multiplication of the value is : " + mult);
}
});
divButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int num1 = Integer.parseInt(editText1.getText().toString());
int num2 = Integer.parseInt(editText2.getText().toString());
int div = num1 / num2;
resultTextView.setText("Division of the value is : " + div);
}
});
moddivButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int num1 = Integer.parseInt(editText1.getText().toString());
int num2 = Integer.parseInt(editText2.getText().toString());
int mdiv = num1 % num2;
resultTextView.setText("Modular Division of the value is : " + mdiv);
}
});
clearButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
editText1.setText("");
editText2.setText("");
resultTextView.setText(" ");
editText1.requestFocus();
}
});
}
}Example : Create an Activity in an Android App to display the selected Color in an EditText when a user selects a color name from a Spinner/Dropdown box using XML & Java in a LinearLayout View.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:contentDescription="@string/app_name"
android:orientation="vertical"
tools:context=".MainActivity"
android:padding="50dp"
android:id="@+id/main">
<Spinner
android:id="@+id/spinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<EditText
android:id="@+id/editText"
android:layout_marginTop="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
strings.xml
<string-array name="spinner_items">
<item>Select Color</item>
<item>Red</item>
<item>Blue</item>
<item>Green</item>
</string-array>
MainActivity.java
package com.example.myapplication2;
// Used for Activity state
import android.os.Bundle;
// Used for View controls
import android.view.View;
// Used for EditText
import android.widget.EditText;
// Used for Spinner
import android.widget.Spinner;
// Used to connect array data with Spinner
import android.widget.ArrayAdapter;
// Used to handle Spinner item selection
import android.widget.AdapterView;
// Used for predefined colors like RED, BLUE, GREEN
import android.graphics.Color;
// Required AndroidX classes
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
// Main Activity class
public class MainActivity extends AppCompatActivity
{
// This method executes when the Activity starts
@Override
protected void onCreate(Bundle savedInstanceState)
{
// Calls the parent Activity onCreate() method
super.onCreate(savedInstanceState);
// Enables edge-to-edge screen display
EdgeToEdge.enable(this);
// Loads activity_main.xml layout
setContentView(R.layout.activity_main);
// Handles system bar spacing like status bar
// and navigation bar
ViewCompat.setOnApplyWindowInsetsListener(
findViewById(R.id.main), (v, insets) -> {
// Gets the size of system bars
Insets systemBars =
insets.getInsets(
WindowInsetsCompat.Type.systemBars()
);
// Adds padding so controls do not overlap system bars
v.setPadding(
systemBars.left,
systemBars.top,
systemBars.right,
systemBars.bottom
);
// Returns the insets
return insets;
});
// Creates an ArrayAdapter and gets Spinner items
// from spinner_items array in strings.xml
ArrayAdapter<CharSequence> spinnerAdapter =
ArrayAdapter.createFromResource(
this,
R.array.spinner_items,
android.R.layout.simple_spinner_item
);
// Sets the layout of Spinner dropdown items
spinnerAdapter.setDropDownViewResource(
android.R.layout.simple_spinner_dropdown_item
);
// Connects Java Spinner object with XML Spinner
Spinner spinner = findViewById(R.id.spinner);
// Attaches the adapter to the Spinner
spinner.setAdapter(spinnerAdapter);
// Connects Java EditText object with XML EditText
EditText editText = findViewById(R.id.editText);
// Executes when an item is selected from Spinner
spinner.setOnItemSelectedListener(
new AdapterView.OnItemSelectedListener() {
// Executes when the user selects an item
@Override
public void onItemSelected(
AdapterView<?> parent,
View view,
int position,
long id) {
// Gets the selected Spinner item as String
String selectedItem =
parent.getItemAtPosition(position)
.toString();
// Checks whether Red is selected
if ("Red".equals(selectedItem))
{
// Clears the EditText
editText.setText("");
// Changes EditText background to Red
editText.setBackgroundColor(Color.RED);
}
// Checks whether Blue is selected
else if ("Blue".equals(selectedItem))
{
// Clears the EditText
editText.setText("");
// Changes EditText background to Blue
editText.setBackgroundColor(Color.BLUE);
}
// Checks whether Green is selected
else if ("Green".equals(selectedItem))
{
// Clears the EditText
editText.setText("");
// Changes EditText background to Green
editText.setBackgroundColor(Color.GREEN);
}
// Executes when no matching color is selected
else
{
// Displays a message in EditText
editText.setText(
"No Color Choice Selection"
);
// Changes EditText background to White
editText.setBackgroundColor(Color.WHITE);
}
}
// Executes when no Spinner item is selected
@Override
public void onNothingSelected(
AdapterView<?> parent)
{
// No action is required here
}
});
} // End of onCreate()
} // End of MainActivity class
NB : Here,
(i) ArrayAdapter, gets the color names from spinner_items in strings.xml.
(ii) spinner.setAdapter(), puts those items into the Spinner/Dropdown box.
(iii) setOnItemSelectedListener(), detects the selected Spinner item.
(iv) getItemAtPosition(position), gets the selected color name. if...else if checks whether the selected item is Red, Blue, or Green.
(v) setBackgroundColor(), changes/sets the background of the EditText.Example : Create an Activity in an Android App to display the Typed Text in the selected color in an EditText when a user selects a color name from a Spinner/Dropdown box using XML & Java in a LinearLayout View.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:contentDescription="@string/app_name"
android:orientation="vertical"
tools:context=".MainActivity"
android:padding="50dp"
android:id="@+id/main">
<Spinner
android:id="@+id/clrSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<EditText
android:id="@+id/editText"
android:layout_marginTop="20dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter any text"
android:textStyle="bold"/>
</LinearLayout>
strings.xml
<string-array name="spinner_items">
<item>Select Color</item>
<item>Red</item>
<item>Blue</item>
<item>Green</item>
</string-array>
MainActivity.java
package com.example.myapplication2;
// Used to store Activity state
import android.os.Bundle;
// Used for View objects
import android.view.View;
// Used for EditText control
import android.widget.EditText;
// Used for Spinner control
import android.widget.Spinner;
// Used to connect array data with Spinner
import android.widget.ArrayAdapter;
// Used to handle Spinner item selection
import android.widget.AdapterView;
// Used for colors such as RED, BLUE, GREEN and BLACK
import android.graphics.Color;
// Used for edge-to-edge screen display
import androidx.activity.EdgeToEdge;
// Base class for the Activity
import androidx.appcompat.app.AppCompatActivity;
// Used for system bar spacing
import androidx.core.graphics.Insets;
// Used for handling View compatibility
import androidx.core.view.ViewCompat;
// Used for handling system window insets
import androidx.core.view.WindowInsetsCompat;
// Main Activity class
public class MainActivity extends AppCompatActivity
{
// This method executes when the Activity starts
@Override
protected void onCreate(Bundle savedInstanceState)
{
// Calls the parent class onCreate() method
super.onCreate(savedInstanceState);
// Enables edge-to-edge screen display
EdgeToEdge.enable(this);
// Loads activity_main.xml file on the screen
setContentView(R.layout.activity_main);
// Creates an ArrayAdapter and gets Spinner items
// from spinner_items array of strings.xml
ArrayAdapter<CharSequence> spinnerAdapter =
ArrayAdapter.createFromResource(
this,
R.array.spinner_items,
android.R.layout.simple_spinner_item
);
// Sets the layout for the Spinner dropdown items
spinnerAdapter.setDropDownViewResource(
android.R.layout.simple_spinner_dropdown_item
);
// Connects Java Spinner object with clrSpinner of XML
Spinner spinner = findViewById(R.id.clrSpinner);
// Connects the ArrayAdapter with Spinner
spinner.setAdapter(spinnerAdapter);
// Connects Java EditText object with editText of XML
EditText editText = findViewById(R.id.editText);
// Executes when an item is selected from the Spinner
spinner.setOnItemSelectedListener(
new AdapterView.OnItemSelectedListener()
{
// Executes when user selects an item
@Override
public void onItemSelected(
AdapterView<?> parent,
View view,
int position,
long id)
{
// Gets the selected Spinner item
// and converts it into String
String selectedItem =
parent.getItemAtPosition(position).toString();
// Checks whether Red is selected
if ("Red".equals(selectedItem))
{
// Changes EditText text color to Red
editText.setTextColor(Color.RED);
}
// Checks whether Blue is selected
else if ("Blue".equals(selectedItem))
{
// Changes EditText text color to Blue
editText.setTextColor(Color.BLUE);
}
// Checks whether Green is selected
else if ("Green".equals(selectedItem))
{
// Changes EditText text color to Green
editText.setTextColor(Color.GREEN);
}
// Executes if Red, Blue or Green is not selected
else
{
// Changes EditText text color to Black
editText.setTextColor(Color.BLACK);
}
}
// Executes when no Spinner item is selected
@Override
public void onNothingSelected(AdapterView<?> parent)
{
// No action is performed
}
});
} // End of onCreate() method
} // End of MainActivity class
NB : Here,
(i) ArrayAdapter, gets the color names from spinner_items in strings.xml.
(ii) spinner.setAdapter(), puts those items into the Spinner/Dropdown box.
(iii) setOnItemSelectedListener(), detects the selected Spinner item.
(iv) getItemAtPosition(position), gets the item selected by the user from the Spinner.
(v) setTextColor(), change/set the text color of the EditText.
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