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Android - setOnClickListener Method, how does it work?



In this article, we are going to learn how to work with setOnClickListener method in Android?
Submitted by Manu Jemini, on November 27, 2017

One of the most usable methods in android is setOnClickListener method which helps us to link a listener with certain attributes.

setOnClickListener is a method in Android basically used with buttons, image buttons etc. You can initiate this method easily like,

public void setOnClickListener(View.OnClickListner)

While invoking this method a callback function will run. One can also create a class for more than one listener, so this can lead you to code reusability.

After making the class you can implement android.view.View.OnClickListener{} method which gives you an override method inherited from super class called onClick(View v){} in which you can easily implement your code.

Java file

package com.example.hp.demo;

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.TextView;

public class MainActivity extends AppCompatActivity {
    EditText name;
    Button click;
    TextView result;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        name=(EditText)findViewById(R.id.name);
        click=(Button)findViewById(R.id.click);
        result=(TextView)findViewById(R.id.result);
        click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                result.setText("Hello "+name.getText());
            }
        });
    }
}

Xml File

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.hp.demo.MainActivity">

    <EditText
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:id="@+id/name"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:hint="Name" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click"
        android:id="@+id/click"
        android:layout_below="@+id/name"
        android:layout_alignParentStart="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="100dp"
        android:text="Result"
        android:id="@+id/result"
        android:layout_below="@+id/click"
        android:layout_alignParentStart="true"
        android:layout_alignParentEnd="true" />
</RelativeLayout>

Manifest File

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.hp.demo">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Output