点击事件的四种写法

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context="sample.android_serialport_api.myapplication.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:text="bt1"
        android:id="@+id/butto1"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="bt2"
        android:id="@+id/butto2"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="bt3"
        android:id="@+id/butto3"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="bt4"
        android:id="@+id/butto4"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="bt5"
        android:id="@+id/butto5"/>
</LinearLayout>

package sample.android_serialport_api.myapplication;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    Button bt1 = null;
    Button bt2 = null;
    Button bt3 = null;
    Button bt4 = null;
    Button bt5 = null;

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

        bt1 = (Button) findViewById(R.id.butto1);
        bt2 = (Button) findViewById(R.id.butto2);
        bt3 = (Button) findViewById(R.id.butto3);
        bt4 = (Button) findViewById(R.id.butto4);
        bt5 = (Button) findViewById(R.id.butto5);
        //方法1：匿名内部类
        bt1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    System.out.println("方式1：按键1");
            }
        });
        
        bt2.setOnClickListener(new Bt2Listener());

        bt3.setOnClickListener(this);
        bt4.setOnClickListener(this);
        bt5.setOnClickListener(this);
    }
    //方法2：内部类继承View.OnClickListener
    private class Bt2Listener implements View.OnClickListener{
        public void onClick(View v) {
            System.out.println("方式2：按键2");
        }
    }
    //方法3：activity继承View.OnClickListener
    public void onClick(View v) {
        System.out.print("方式3:");
        int i = v.getId();
        switch(i){
            case R.id.butto3:
                System.out.println("按键3");
                break;
            case R.id.butto4:
                System.out.println("按键4");
                break;
            case R.id.butto5:
                System.out.println("按键5");
                break;
            default:break;
        }
    }
}