OnClickListener 実装例

class BasicPatternActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        button.setOnClickListener(object : View.OnClickListener {

            override fun onClick(v: View?) {

                // TODO: ボタンクリック時の処理

            }

        })

    }

}

class Pattern1Activity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        button.setOnClickListener {

            // TODO: ボタンクリック時の処理

        }

    }

}

class Pattern2Activity : AppCompatActivity(), View.OnClickListener {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_pattern2)

        for (button in listOf(button1, button2, button3)) {

            button.setOnClickListener(this)

        }

    }

    override fun onClick(v: View?) {

        if (v is Button) {

            val message: String = when (v.id) {

                R.id.button1 -> "button1 clicked!"

                R.id.button2 -> "button2 clicked!"

                else -> "button3 clicked!"

            }

            Toast.makeText(applicationContext, message, Toast.LENGTH_SHORT).show()

        }

    }

}

class Pattern3Activity : AppCompatActivity() {

    private val buttonOnClickListener = View.OnClickListener {

        // TODO: ボタンクリック時の処理

    }

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        button.setOnClickListener(buttonOnClickListener)

    }

}