Button OnClickListner in Android

 In this post I will show the basic function of a Button, whenever a button is pressed a text message will be displayed.

Step1-  First Create a Android Project and name it as Button.

Step2 - Go to res folder and then to layout and in .xml file copy the code given below


 

1:  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
2:    xmlns:tools="http://schemas.android.com/tools"  
3:    android:layout_width="match_parent"  
4:    android:layout_height="match_parent"  
5:    android:paddingBottom="@dimen/activity_vertical_margin"  
6:    android:paddingLeft="@dimen/activity_horizontal_margin"  
7:    android:paddingRight="@dimen/activity_horizontal_margin"  
8:    android:paddingTop="@dimen/activity_vertical_margin"  
9:    tools:context=".MainActivity" >  
10:    <Button  
11:      android:id="@+id/button1"  
12:      android:layout_width="wrap_content"  
13:      android:layout_height="wrap_content"  
14:      android:layout_alignParentBottom="true"  
15:      android:layout_marginBottom="179dp"  
16:      android:layout_marginLeft="46dp"  
17:      android:layout_toRightOf="@+id/textView1"  
18:      android:text="Button" />  
19:    <TextView  
20:      android:id="@+id/textView2"  
21:      android:layout_width="wrap_content"  
22:      android:layout_height="wrap_content"  
23:      android:layout_alignTop="@+id/button1"  
24:      android:layout_centerHorizontal="true"  
25:      android:layout_marginTop="108dp"  
26:      android:text="TextView" />  
27:  </RelativeLayout>  

Step 3- Then go the /scr directory and in the MainActivity.java  copy the code shown below.

1:   package com.example.button;  
2:  import android.app.Activity;  
3:  import android.os.Bundle;  
4:  import android.view.View;  
5:  import android.widget.Button;  
6:  import android.widget.TextView;  
7:  public class MainActivity extends Activity {  
8:  Button Btn;  
9:   TextView tv;  
10:    @Override  
11:    protected void onCreate(Bundle savedInstanceState) {  
12:      super.onCreate(savedInstanceState);  
13:      setContentView(R.layout.activity_main);  
14:      Btn =(Button) findViewById(R.id.button1);  
15:      tv = (TextView) findViewById(R.id.textView2);  
16:      Btn.setOnClickListener(new View.OnClickListener() {  
17:        @Override  
18:        public void onClick(View v) {  
19:        tv.setText("Welcome to android world");  
20:        }  
21:      });  
22:    }  
23:  }  

Now  upload it to your emulator or phone and you can see whenever the the button is clicked the message is displayed in the Textview.

The link for the code - https://www.dropbox.com/s/oig3o79z37648pa/Button.zip