如何在 GameActivity 中使用来自 SurfaceView 内部的 Toast 消息？

Question

以下是我项目中 GameActivity 和 GameView 的片段： GameActivity.kt

class GameActivity : Activity() {
    private var gameView: GameView? = null

    // We override the oncreate to add the gameview which will be showing the game
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        var display = windowManager.defaultDisplay

        val size = Point()
        display.getSize(size)

        gameView = GameView(this, size)
        setContentView(gameView)
    }
}

GameView.kt

class GameView(context: Context, private val size: Point) : SurfaceView(context), Runnable {

    private val gameThread = Thread(this)

    ...

    private fun prepareLevel() {}

    ...
    private fun update (fps: Long) {
    if (RectF.intersects(powerup.position, player.position)) {
        Toast.makeText(context, "Powerup intersects", Toast.LENGTH_SHORT).show()
    }
    }
    ...
}

问题是当交集发生时代码中断并出现以下错误：

E/AndroidRuntime: FATAL EXCEPTION: Thread-2
    Process: com.example.sacredanimals, PID: 3367
    java.lang.RuntimeException: Can't toast on a thread that has not called Looper.prepare()
        at android.widget.Toast$TN.<init>(Toast.java:390)
        at android.widget.Toast.<init>(Toast.java:114)
        at android.widget.Toast.makeText(Toast.java:277)
        at android.widget.Toast.makeText(Toast.java:267)
        at com.example.sacredanimals.GameView.update(GameView.kt:96)
        at com.example.sacredanimals.GameView.run(GameView.kt:78)
        at java.lang.Thread.run(Thread.java:764)

我进行了一些调试，问题的发生可能是因为应该在主线程而不是子线程之一上调用 Toast 消息，如 link 中所建议：但是，对于我想从 SurfaceView

内部调用 Toast.message 的情况，我无法解决这个问题

Answer 1

Toast.makeText() 只能从 Main/UI 线程调用。 Looper.getMainLooper() 帮你实现：

Handler(Looper.getMainLooper()).post { 
     Toast.makeText(context, "Powerup intersects", Toast.LENGTH_SHORT).show()
}

如何在 GameActivity 中使用来自 SurfaceView 内部的 Toast 消息？

How to use Toast message from inside SurfaceView inside GameActivity?

surfaceview

android-activity

kotlin

android-toast

kotlin-coroutines