Android Button with Examples

In Android example, Button in android is a user interface control used to perform an action whenever a user clicks or clicks on it.
Generally, the buttons in Android will contain a text or an icon or both and perform an action when the user touches it.
The following is a representative image of the use of android circle button apps.
Android buttons for example
In Android, we have a different type of button available to use based on our requirements, which is ImageButton, ToggleButton, RadioButton.
In Android, we can create a Button control in two ways in an XML layout file or create it in an Activity file programmatically.

Create Button in XML Layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/addBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add" />
</LinearLayout>

Create Button Control in Activity

In android, we can create circle button android control programmatically in activity file based on our requirements. 

Following is the example of creating Button control dynamically in activity file.

LinearLayout layout = (LinearLayout)findViewById(R.id.l_layout);
Button btn = new Button(this);
btn.setText("Test");
layout.addView(btn);

Android Handle Button Click Events

Generally, whenever the user clicks on a android round button, the Button object will receives an on-click event.
In android, we can define button click event in two ways either in XML layout file or create it in Activity file programmatically.

Define Button Click Event in XML Layout File

We can define click event handler for button by adding android:onClick attribute to the <Button> element in our XML layout file.
The value of android:onClick attribute must be the name of method which we need to call in response to a click event and the Activity file which hosting XML layout must implement the corresponding method.
Following is the example of defining a button click event using android:onClick attribute in XML layout file.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
        <Button
        android:id="@+id/addBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        android:onClick="addOperation"/>
</LinearLayout>

Android Button Example 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/fstTxt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="100dp"
        android:layout_marginTop="150dp"
        android:text="First Number" />
    <EditText
        android:id="@+id/firstNum"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="100dp"
        android:ems="10" />
    <TextView
        android:id="@+id/secTxt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Second Number"
        android:layout_marginLeft="100dp" />
    <EditText
        android:id="@+id/secondNum"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="100dp"
        android:ems="10" />
    <Button
        android:id="@+id/addBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="100dp"
        android:text="Add" />
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText firstNum = (EditText)findViewById(R.id.firstNum);
        final EditText secNum = (EditText)findViewById(R.id.secondNum);
        Button btnAdd = (Button)findViewById(R.id.addBtn);
        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(firstNum.getText().toString().isEmpty() || secNum.getText().toString().isEmpty())
                {
                    Toast.makeText(getApplicationContext(), "Please fill all the fields", Toast.LENGTH_SHORT).show();
                }
                else {
                    int num1 = Integer.parseInt(firstNum.getText().toString());
                    int num2 = Integer.parseInt(secNum.getText().toString());
                    Toast.makeText(getApplicationContext(), "SUM = " + (num1 + num2), Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
} 

Output of Android Button Example