How to use an OnClickListener In Java
You can also declare the click event handler programmatically rather than in an XML layout. This event handler code is mostly preferred because it can be used in both Activities and Fragments.
There are two ways to do this event handler programmatically :
- Implementing View.OnClickListener in your Activity or fragment.
- Creating new anonymous View.OnClickListener.
Layout for all the cases will be same which is mentioned below as acitivity_main.xml file:
<RelativeLayout
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.sample.MainActivity" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/button_send" />
</RelativeLayout>
1. Implementing View.OnClickListener in your Activity or fragment
To implement View.OnClickListener in your Activity or Fragment, you have to override onClick method on your class.
- Firstly, link the button in xml layout to java by calling
findViewById()method.R.id.button_sendrefers the button in XML.
mButton.setOnClickListener(this); means that you want to assign listener for your Button “on this instance” this instance represents OnClickListener and for this reason your class have to implement that interface.
MainActivity code:
package com.example.handling_button_java;
import android.annotation.SuppressLint;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Button mButton;
private TextView mTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mButton = findViewById(R.id.button_send);
mButton.setOnClickListener(this);
mTextView = findViewById(R.id.text_after);
}
// Override the onClick Method and return the result
// Accordingly
@Override
public void onClick(View view) {
if (view.getId()==R.id.button_send) {
if (mTextView != null) {
mTextView.setText("This is the after Result");
}
}
}
}
If you have more than one button click event, you can use switch case to identify which button is clicked.
2. Creating Anonymous View.OnClickListener
Link the button from the XML by calling findViewById() method and set the onClick listener by using setOnClickListener() method.
MainActivity code:
package com.example.handling_button_java;
import android.annotation.SuppressLint;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private Button mButton;
private TextView mTextView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Putting vaules in mButton and mTextView
mButton = findViewById(R.id.button_send);
mTextView = findViewById(R.id.text_after);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view)
{
// Operations Performed On Clicking the Button
// Are Done Here
mTextView.setText("This is the after Result");
}
});
}
}
setOnClickListener takes an OnClickListener object as the parameter. Basically it’s creating an anonymous subclass OnClickListener in the parameter. It’s like the same in java when you can create a new thread with an anonymous subclass.
Output of the Programs:
After Clicking the Button the Result Will be as mentioned below:
Handling Click Events in Button in Java Android
Click Events are one of the basic operations often used in Java Android Development to create Java Android Applications. In this article, we will learn about how to Handle Click Events in Button in Android Java.
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