【Android】ダイアログのサンプルコード

import android.app.AlertDialog
import android.app.Dialog
import android.content.Context
import android.graphics.Color
import android.graphics.drawable.ColorDrawable
import android.os.Bundle
import android.widget.CheckBox
import android.widget.CompoundButton
import androidx.fragment.app.DialogFragment

/**
 * アクティビティやフラグメントでAlertDialogを直接利用するとリークの原因になる
 * 代わりにこのフラグメントを利用すればOK
 */
open class AlertDialogFragment : DialogFragment() {

    // 親がFragmentのみの場合はsetFragmentResultListenerを使うことでlistenerは不要となるが、
    // 実際は親がActivityの可能性もあるのでlistenerの導入が必須
    internal lateinit var listener: AlertDialogListener

    interface AlertDialogListener {
        fun onDialogPositiveClick(dialog: DialogFragment)
        fun onDialogNegativeClick(dialog: DialogFragment)
        fun onDialogCheckBoxChange(isChecked: Boolean)
    }

    var icon: Int? = null
    var title: String? = null
    var message: String? = null
    var positiveButtonText: String? = null
    var negativeButtonText: String? = null
    var checkBoxText: String? = null

    // クラス単位で一意かつ静的な値
    companion object {
        const val TAG = "AlertDialogFragment"
        private const val ICON_KEY = "ICON_KEY"
        private const val TITLE_KEY = "TITLE_KEY"
        private const val MESSAGE_KEY = "MESSAGE_KEY"
        private const val POSITIVE_BUTTON_TEXT_KEY = "POSITIVE_BUTTON_TEXT_KEY"
        private const val NEGATIVE_BUTTON_TEXT_KEY = "NEGATIVE_BUTTON_TEXT_KEY"
        private const val CHECK_BOX_TEXT_KEY = "CHECK_BOX_TEXT_KEY"
    }

    // Builderを使わないと画面回転時に変数の値が初期化してしまう
    class Builder {
        private val bundle = Bundle()

        fun setIcon(icon: Int): Builder {
            return this.apply { bundle.putInt(ICON_KEY, icon) }
        }

        fun setTitle(title: String): Builder {
            return this.apply { bundle.putString(TITLE_KEY, title) }
        }

        fun setMessage(message: String): Builder {
            return this.apply { bundle.putString(MESSAGE_KEY, message) }
        }

        fun setPositiveButtonText(text: String): Builder {
            return this.apply { bundle.putString(POSITIVE_BUTTON_TEXT_KEY, text) }
        }

        fun setNegativeButtonText(text: String): Builder {
            return this.apply { bundle.putString(NEGATIVE_BUTTON_TEXT_KEY, text) }
        }

        fun setCheckBoxText(text: String): Builder {
            return this.apply { bundle.putString(CHECK_BOX_TEXT_KEY, text) }
        }

        fun build(): AlertDialogFragment {
            return AlertDialogFragment().apply { arguments = bundle }
        }
    }

    override fun onAttach(context: Context) {
        super.onAttach(context)
        try {
            listener = getParentFragmentOrActivity() as AlertDialogListener;
        } catch (e: ClassCastException) {
            throw ClassCastException(("$context must implement AlertDialogListener"))
        }
    }

    open fun getParentFragmentOrActivity(): Any? {
        return parentFragment ?: activity
    }

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        // ダイアログの背景を透過にする
        val dialog = Dialog(requireContext())
        dialog.window?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT))

        val alertDialog = AlertDialog.Builder(context)

        // Bundleに渡した値を取り出す
        arguments?.let { bundle ->
            icon = bundle.getInt(ICON_KEY, -1)
            if (icon != -1) alertDialog.setIcon(icon!!)

            title = bundle.getString(TITLE_KEY, "")
            if (title != "") alertDialog.setTitle(title)

            message = bundle.getString(MESSAGE_KEY, "")
            if (message != "") alertDialog.setMessage(Html.fromHtml(message))

            positiveButtonText = bundle.getString(POSITIVE_BUTTON_TEXT_KEY)
            if (positiveButtonText != "") {
                alertDialog.setPositiveButton(positiveButtonText) { dialog, which ->
                    listener.onDialogPositiveClick(this)
                }
            }

            negativeButtonText = bundle.getString(NEGATIVE_BUTTON_TEXT_KEY)
            if (negativeButtonText != "") {
                alertDialog.setNegativeButton(negativeButtonText) { dialog, which ->
                    listener.onDialogNegativeClick(this)
                }
            }

            checkBoxText = bundle.getString(CHECK_BOX_TEXT_KEY)
            checkBoxText?.let {
                val inflater = requireActivity().layoutInflater
                val root = inflater.inflate(R.layout.dialog_alert_custom, null)
                val checkBox = root.findViewById<CheckBox>(R.id.checkbox)
                checkBox.text = it
                checkBox.setOnCheckedChangeListener { buttonView: CompoundButton?, isChecked: Boolean ->
                    listener.onDialogCheckBoxChange(isChecked)
                }
                alertDialog.setView(root)
            }
        }

        return alertDialog.create()
    }

    override fun onStart() {
        super.onStart()
        val alertDialog = dialog as AlertDialog?
        if (alertDialog != null) (alertDialog.findViewById<View>(android.R.id.message) as TextView).movementMethod = LinkMovementMethod.getInstance()
    }
}