Basic onClickListener

Its a very basic example to implement onClickListener for Button:
- Button A, define onClickListener as anonymous class.
- Button B1 and B2: define onClickListener class.
- Button C1 and C2: assign callback function in XML.


activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
 
 android_id="@+id/background"
 android_layout_width="match_parent"
 android_layout_height="match_parent"
 android_padding="16dp"
 android_orientation="vertical"
 android_onClick="onBackgroundClickedCallback"
 tools_context="com.blogspot.android_er.androidclicklistener.MainActivity">

 <TextView
 android_layout_width="wrap_content"
 android_layout_height="wrap_content"
 android_layout_gravity="center_horizontal"
 android_autoLink="web"
 android_text="http://android-er.blogspot.com/"
 android_textStyle="bold" />

 <Button
 android_id="@+id/buttona"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_text="Button A: anonymous onClickListener"/>

 <Button
 android_id="@+id/buttonb1"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_text="Button B1: onClickListener"/>

 <Button
 android_id="@+id/buttonb2"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_text="Button B2: onClickListener"/>

 <Button
 android_id="@+id/buttonc1"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_onClick="onClickCallback"
 android_text="Button C1: define callback in XML"/>

 <Button
 android_id="@+id/buttonc2"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_onClick="onClickCallback"
 android_text="Button C2: define callback in XML"/>

 <TextView
 android_id="@+id/info"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_textSize="28dp"/>
</LinearLayout>

MainActivity.java

package com.blogspot.android_er.androidclicklistener;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

 Button btnA, btnB1, btnB2, btnC1, btnC2;
 TextView textInfo;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 btnA = (Button)findViewById(R.id.buttona);
 btnB1 = (Button)findViewById(R.id.buttonb1);
 btnB2 = (Button)findViewById(R.id.buttonb2);
 btnC1 = (Button)findViewById(R.id.buttonc1);
 btnC2 = (Button)findViewById(R.id.buttonc2);
 textInfo = (TextView) findViewById(R.id.info);

 btnA.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Toast.makeText(MainActivity.this,
 "Button A Clicked: implement anonymous onClickListener",
 Toast.LENGTH_LONG).show();
 textInfo.setText(v.toString());
 }
 });

 btnB1.setOnClickListener(btnBOnClickListener);
 btnB2.setOnClickListener(btnBOnClickListener);
 }

 //set by calling setOnClickListener()
 View.OnClickListener btnBOnClickListener = new View.OnClickListener() {
 @Override
 public void onClick(View v) {

 if(v.getId() == R.id.buttonb1){
 Toast.makeText(MainActivity.this,
 "Button B1 Clicked: implement onClickListener",
 Toast.LENGTH_LONG).show();
 }else if((v.getId() == R.id.buttonb2)){
 Toast.makeText(MainActivity.this,
 "Button B2 Clicked: implement onClickListener",
 Toast.LENGTH_LONG).show();
 }

 textInfo.setText(v.toString());
 }
 };

 //define in XML
 public void onClickCallback(View v){
 if(v.getId() == R.id.buttonc1){
 Toast.makeText(MainActivity.this,
 "Button C1 Clicked: callback assign in XML",
 Toast.LENGTH_LONG).show();
 }else if((v.getId() == R.id.buttonc2)){
 Toast.makeText(MainActivity.this,
 "Button C2 Clicked: callback assign in XML",
 Toast.LENGTH_LONG).show();
 }

 textInfo.setText(v.toString());
 }

 //define in XML
 public void onBackgroundClickedCallback(View v){
 Toast.makeText(MainActivity.this,
 "Background Clicked",
 Toast.LENGTH_LONG).show();
 textInfo.setText(v.toString());
 }
}