Android Button with Examples

In android, Button is a user interface control which is used to perform an action whenever the user click or tap on it.

Generally, Buttons in android will contains a text or an icon or both and perform an action when user touches it.

Following is the pictorial representation of using Buttons in android applications.

In android, we have a different type of buttons available to use based on our requirements, those are ImageButton, ToggleButton, RadioButton.

In android, we can create a Button control in two ways either in XML layout file or create it in Activity file programmatically.

Create Button in XML Layout File

Following is the sample way to define Button control in XML layout file in android application.

<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>

If you observe above code snippet, here we defined Button control in xml layout file.

Create Button Control in Activity File

In android, we can create Button 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 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>

In Activity that hosts our XML layout file, we need to implement click event method like as shown below

/** Called when the user touches the button */public void addOperation(View view) {
    // Do something in response to button click}

Define Button Click Event in Activity File

In android, we can define button click event programmatically in Activity file rather than XML layout file.

To define button click programmatically, create View.OnClickListener object and assign it to the button by calling setOnClickListener(View.OnClickListener) like as shown below.

Button btnAdd = (Button)findViewById(R.id.addBtn);
btnAdd.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {

// Do something in response to button click}
});
}

This is how we can handle button click events in android applications based on our requirements.

Android Button Control Attributes

Following are the some of commonly used attributes related to Button control in android applications.

Attribute	Description
android:id	It is used to uniquely identify the control
android:gravity	It is used to specify how to align the text like left, right, center, top, etc.
android:text	It is used to set the text.
android:textColor	It is used to change the color of text.
android:textSize	It is used to specify the size of text.
android:textStyle	It is used to change the style (bold, italic, bolditalic) of text.
android:background	It is used to set the background color for button control.
android:padding	It is used to set the padding from left, right, top and bottom.
android:drawableBottom	It’s a drawable to be drawn to the below of text.
android:drawableRight	It’s a drawable to be drawn to the right of text.
android:drawableLeft	It’s a drawable to be drawn to the left of text.

Android Button Control Example

Following is the example of defining a one Button and two EditText controls in LinearLayout to get the data of EditText controls when click on Button in android application.

Create a new android application using android studio and give names as ButtonExample. In case if you are not aware of creating an app in android studio check this article Android Hello World App.

Now open an activity_main.xml file from \res\layout path and write the code like as shown below

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>

If you observe above code we created one Button, two TextView controls and two EditText controls in XML Layout file. 

Once we are done with creation of layout with required control, we need to load the XML layout resource from our activity onCreate() callback method, for that open main activity file MainActivity.java from \java\com.tutlane.buttonexample path and write the code like as shown below.

MainActivity.java

package com.tutlane.buttonexample;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;
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();
                }
            }
        });
    }
}

If you observe above code we are calling our layout using setContentView method in the form of R.layout.layout_file_name in our activity file. Here our xml file name is activity_main.xml so we used file name activity_main and we are getting the values from two EditText controls on Button click and performing an addition operation.

Generally, during the launch of our activity, onCreate() callback method will be called by android framework to get the required layout for an activity.

Output of Android Button Example

When we run above example using android virtual device (AVD) we will get a result like as shown below.

This is how we can use Button control in android applications to perform required operations on button tap or click based on our requirements.