FacebookのMessengerみたいなアプリを作る

# はじめに
この記事は[ロボP Advent Calendar 2018](https://qiita.com/advent-calendar/2018/robop)の2日目の記事です．

# FBのMessengerって？
メッセージが来ると横にプヨって出てくるやつ
**ChatHead**って言うらしい。
![chathead.jpg](https://qiita-image-store.s3.amazonaws.com/0/126115/505be232-5a6a-f239-8efb-0db93fa25221.jpeg)

# 作る
## 画面に残るViewを作る
WindowManagerをServiceで動かして実装します。
通常のアプリケーションより高いレイヤーに描画するイメージ。

### Permission
画面を重ねて描画するための`SYSTEM_ALERT_WINDOW`

```AndroidManifest.xml
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
```

### MainActivity
無くてもいけますが、テストしやすいため今回は使います。

```MainActivity.kt
class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //API23から権限が必要
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkPermission()
        }

        findViewById<TextView>(R.id.text).setOnClickListener {
            val intent = Intent(application, OverlayService::class.java)
            // Serviceの開始
            // API26以上はNotificationが入るため処理が別
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                startForegroundService(intent)
            } else {
                startService(intent)
            }
        }
    }

    @RequiresApi(Build.VERSION_CODES.M)
    fun checkPermission() {
        if (!Settings.canDrawOverlays(this)) {
            val intent = Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                    Uri.parse("package:$packageName"))
            startActivityForResult(intent, 1000)
        }
    }
}
```
**Android8.0(Oreo|API26)**からは画面上に重ねて描画すると
Notificationが出るようになったため、`startForegroundService()`でServiceを開始します。

```activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/text"
        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" />

</android.support.constraint.ConstraintLayout>
```
レイアウトは特に変えてません。

### OverlayService
こいつが今回の肝です。

```OverlayService.kt
class OverlayService : Service() {
    private var view: View? = null
    private var windowManager: WindowManager? = null
    private var dpScale: Int = 0

    override fun onCreate() {
        super.onCreate()

        dpScale = resources.displayMetrics.density.toInt()
    }

    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {

        val context = applicationContext
        val channelId = "default"
        val title = context.getString(R.string.app_name)

        val pendingIntent = PendingIntent.getActivity(context, 0, intent,
                PendingIntent.FLAG_UPDATE_CURRENT)

        //8.0(Oreo)以上用のNotification設定
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            val channel = NotificationChannel(
                    channelId, title, NotificationManager.IMPORTANCE_DEFAULT)

            if (notificationManager != null) {
                notificationManager.createNotificationChannel(channel)

                val notification = Notification.Builder(context, channelId)
                        .setContentTitle(title)
                        .setSmallIcon(android.R.drawable.btn_star)
                        .setContentText("APPLICATION_OVERLAY")
                        .setAutoCancel(true)
                        .setContentIntent(pendingIntent)
                        .setWhen(System.currentTimeMillis())
                        .build()

                startForeground(1, notification)
            }
        }

        // inflaterの生成
        val layoutInflater = LayoutInflater.from(this)

        //8.0(Oreo)以上のみレイヤータイプを分ける
        val typeLayer = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
            WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
        else
            WindowManager.LayoutParams.TYPE_SYSTEM_ALERT

        windowManager = applicationContext
                .getSystemService(Context.WINDOW_SERVICE) as WindowManager

        val params = WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                typeLayer,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                PixelFormat.TRANSLUCENT)

        val nullParent: ViewGroup? = null
        view = layoutInflater.inflate(R.layout.layout_overlay, nullParent)
        //クリックで解除できるように
        view?.findViewById<Button>(R.id.btn_overlay)
                ?.setOnClickListener {
                    // Viewを削除
                    windowManager!!.removeView(view)
                }

        // ViewにTouchListenerを設定する
        view!!.setOnTouchListener { v, event ->
            Log.d("debug", "onTouch")
            if (event.action == MotionEvent.ACTION_DOWN) {
                Log.d("debug", "ACTION_DOWN")
            }
            if (event.action == MotionEvent.ACTION_UP) {
                Log.d("debug", "ACTION_UP")

                view!!.performClick()

                stopSelf()
            }
            false
        }

        // Viewを画面上に追加
        windowManager!!.addView(view, params)

        return super.onStartCommand(intent, flags, startId)
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d("debug", "onDestroy")
        // Viewを削除
        windowManager!!.removeView(view)
    }

    override fun onBind(intent: Intent): IBinder? {
        return null
    }
```

レイヤータイプが8.0以上とそれ以外で異なるので、注意してください。

```Kotlin

//8.0(Oreo)以上のみレイヤータイプを分ける
val typeLayer = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
    WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
else
    WindowManager.LayoutParams.TYPE_SYSTEM_ALERT
```

ここで描画するViewはここでinflateしてます。

```Kotlin
view = layoutInflater.inflate(R.layout.layout_overlay, nullParent)
```

```layout_overlay.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <Button
        android:id="@+id/btn_overlay"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ボタン"/>

</android.support.constraint.ConstraintLayout>
```

### 実行！
どこに行ってもボタンが出るようになったかと思います。
<img src="https://qiita-image-store.s3.amazonaws.com/0/126115/1fca6b61-c378-e0f0-1713-c5c55cb80934.png" width=50%>

## UIをそれっぽくする
今回はMessengerの代わりにWebを出すようにします。

### Permission
```AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET"/>
```
webViewを使うので`INTERNET`を追加します。

### OverlayService
```OverlayService.kt
class OverlayService : Service() {
    private var view: View? = null
    private var windowManager: WindowManager? = null
    private var dpScale: Int = 0
    private var typeLayer: Int = 0

    private var isBigView: Boolean = false

    var overlayImgV: ImageView? = null
    var webV: WebView? = null

    override fun onCreate() {
        super.onCreate()

        dpScale = resources.displayMetrics.density.toInt()
    }

    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {

        val context = applicationContext
        val channelId = "default"
        val title = context.getString(R.string.app_name)

        val pendingIntent = PendingIntent.getActivity(context, 0, intent,
                PendingIntent.FLAG_UPDATE_CURRENT)

        //8.0(Oreo)以上用のNotification設定
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            val channel = NotificationChannel(
                    channelId, title, NotificationManager.IMPORTANCE_DEFAULT)

            if (notificationManager != null) {
                notificationManager.createNotificationChannel(channel)

                val notification = Notification.Builder(context, channelId)
                        .setContentTitle(title)
                        .setSmallIcon(android.R.drawable.btn_star)
                        .setContentText("APPLICATION_OVERLAY")
                        .setAutoCancel(true)
                        .setContentIntent(pendingIntent)
                        .setWhen(System.currentTimeMillis())
                        .build()

                startForeground(1, notification)
            }
        }

        // inflaterの生成
        val layoutInflater = LayoutInflater.from(this)

        //8.0(Oreo)以上のみレイヤータイプを分ける
        typeLayer = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
            WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
        else
            WindowManager.LayoutParams.TYPE_SYSTEM_ALERT

        windowManager = applicationContext
                .getSystemService(Context.WINDOW_SERVICE) as WindowManager

        val params = WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                typeLayer,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                PixelFormat.TRANSLUCENT)

        params.gravity = Gravity.TOP or Gravity.LEFT

        val nullParent: ViewGroup? = null
        view = layoutInflater.inflate(R.layout.layout_overlay, nullParent)
        //クリックで解除できるように
        view?.findViewById<Button>(R.id.btn_overlay)
                ?.setOnClickListener {
                    // Viewを削除
                    windowManager!!.removeView(view)
                }
        overlayImgV = view?.findViewById<ImageView>(R.id.ic_overlay)
        overlayImgV?.setOnClickListener {
            if (!isBigView) {
                openBigView()
            } else {
                closeBigView()
            }
        }
        webV=view?.findViewById<WebView>(R.id.web_overlay)
        webV?.visibility=View.GONE
        webV?.webViewClient = WebViewClient()
        webV?.loadUrl("https://www.google.com/")

        // ViewにTouchListenerを設定する
        view!!.setOnTouchListener { v, event ->
            Log.d("debug", "onTouch")
            if (event.action == MotionEvent.ACTION_DOWN) {
                Log.d("debug", "ACTION_DOWN")
            }
            if (event.action == MotionEvent.ACTION_UP) {
                Log.d("debug", "ACTION_UP")

                view!!.performClick()

                stopSelf()
            }
            false
        }

        // Viewを画面上に追加
        windowManager!!.addView(view, params)

        return super.onStartCommand(intent, flags, startId)
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d("debug", "onDestroy")
        // Viewを削除
        windowManager!!.removeView(view)
    }

    override fun onBind(intent: Intent): IBinder? {
        return null
    }

    private fun openBigView() {
        val params = WindowManager.LayoutParams(
                WindowManager.LayoutParams.MATCH_PARENT,
                WindowManager.LayoutParams.MATCH_PARENT,
                typeLayer,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                PixelFormat.TRANSLUCENT)
        params.gravity = Gravity.TOP or Gravity.LEFT
        windowManager?.updateViewLayout(view, params)

        val cx = overlayImgV?.left!! + overlayImgV?.width!! / 2
        val cy = overlayImgV?.top!! + overlayImgV?.height!! / 2
        val radius = Math.max(webV?.width!!, webV?.height!!)

        val anim = android.view.ViewAnimationUtils.createCircularReveal(webV, cx, cy, 0f, radius.toFloat())

        webV?.visibility = View.VISIBLE
        TransitionManager.beginDelayedTransition(webV?.rootView as ViewGroup)
        anim.start()

        isBigView = true
    }

    private fun closeBigView() {

        val cx = overlayImgV?.left!! + overlayImgV?.width!! / 2
        val cy = overlayImgV?.top!! + overlayImgV?.height!! / 2
        val radius = Math.max(webV?.width!!, webV?.height!!)

        val anim = android.view.ViewAnimationUtils.createCircularReveal(webV, cx, cy, radius.toFloat(), 0f)
        anim.addListener(object : AnimatorListenerAdapter() {
            override fun onAnimationEnd(animation: Animator) {
                super.onAnimationEnd(animation)
                webV?.visibility = View.GONE
                TransitionManager.beginDelayedTransition(webV?.rootView as ViewGroup)

                val params = WindowManager.LayoutParams(
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        typeLayer,
                        WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                        PixelFormat.TRANSLUCENT)
                params.gravity = Gravity.TOP or Gravity.LEFT
                windowManager?.updateViewLayout(view, params)
            }
        })
        anim.start()

        isBigView = false
    }
}
```
アニメーションを追加しました。

```layout_overlay.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="wrap_content"
    android:layout_height="wrap_content">

    <WebView
        android:id="@+id/web_overlay"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:visibility="gone"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:ignore="WebViewLayout" />

    <ImageView
        android:id="@+id/ic_overlay"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:src="@mipmap/ic_launcher"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/btn_overlay"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:background="@drawable/bg_oval"
        android:text="×"
        android:textColor="#ffffff"
        android:textSize="20dp"
        app:layout_constraintEnd_toEndOf="@id/ic_overlay"
        app:layout_constraintTop_toTopOf="@id/ic_overlay" />

</android.support.constraint.ConstraintLayout>
```
ButtonをImageViewに買えて×ボタンとWebViewを追加しました。

### 実行！  
<img src="https://qiita-image-store.s3.amazonaws.com/0/126115/de2ed1fe-54c0-0ddb-d513-1263e5cb798c.gif" width=50%>

# 参考
[nyanのアプリ開発 | WindowManagerを使ってServiceから画像を表示させ続ける](https://akira-watson.com/android/windowmanager.html)

[AndroidでViewを他のアプリの上に表示する (APIバージョン別 対応方法まとめ)](https://qiita.com/tokisuzume/items/466fc9dc471013e4b6dc)

めっちゃ参考にしました。ありがとうございます。