Question

我有以下代码：

override fun onCreate(savedInstanceState: Bundle?) {
    ...
    fab_action.setOnClickListener(actionSetMyLocationEnable) //passing my lambda
}

private val actionSetMyLocationEnable: (View) -> Unit = { it as FloatingActionButton
    it.isSelected = !it.isSelected
    setMyLocationEnable(it.isSelected) //this call work fine
}

private fun setMyLocationEnable(enable: Boolean) {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(
                this,
                arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
                PERMISSION_REQUEST_ACCESS_FINE_LOCATION)
        return //and this return work nice too
    }
    mMap.isMyLocationEnabled = enable
}

但是，当我按以下方式应用它时：

private val actionSetMyLocationEnable: (View) -> Unit = { it as FloatingActionButton
    it.isSelected = !it.isSelected
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(
                this,
                arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
                PERMISSION_REQUEST_ACCESS_FINE_LOCATION)
        return //error 1
    }
    mMap.isMyLocationEnabled = it.isSelected //error 2
}

我遇到了两个错误：

错误1。

此处不允许“返回”

错误2。

呼叫需要许可，但可能会被用户拒绝：代码应明确检查权限是否可用（带有 checkPermission）或显式处理潜在的SecurityException

我知道每个错误的含义，但是

我的问题是：为什么我的代码在lambda表达式之外无法工作，而在lambda表达式之外却不能工作？而我该如何解决呢？

已更新

@Rene Ferrari's solution解决了错误1 。非常感谢@Rene Ferrari

Answer 1

基于mTak的答案，我的解决方法是：

private val actionSetMyLocationEnable: (View) -> Unit = returnHere@{ it as FloatingActionButton
    it.isSelected = !it.isSelected
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(
                this,
                arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
                PERMISSION_REQUEST_ACCESS_FINE_LOCATION)
        return@returnHere //error 1
    }
    mMap.isMyLocationEnabled = it.isSelected //error 2
}

您基本上可以定义要返回的标签。该标签可以命名为课程关键字以外的任何名称。在此示例中，我将其命名为returnHere

代码在lambda表达式之外运行，但不能在内部运行

1 个答案: