更改片段中的屏幕亮度

Question

当我打开一些放置在我的活动中的片段时，我想更改屏幕的亮度，因此我在 onActivityCreated 中放置了此代码（我也尝试将其放置在 onResume 中）。但是当用户关闭此片段时，我想将屏幕恢复到以前的亮度。但目前亮度适用于所有活动。如何仅对片段应用脆性？或者记录亮度结果并在片段关闭时重新运行？

class BrightnessFragment : Fragment(), Injectable {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        appCompatActivity = activity as AppCompatActivity

        val lp = activity!!.window.attributes
        lp.screenBrightness = 1F
        activity!!.window.attributes = lp
    }

    override fun onResume() {
        super.onResume()
    }
}

Answer 1

您可以将以前的亮度存储在Fragment 内的变量中。当Fragment被移除时，它会调用onDestroy()，这是重置亮度的好时机。

附带说明，当您使用 Kotlin 编写代码时，请尽量避免使用 !!。如果它为空，你应该优雅地处理这个案例。使用?.let，您可以编写它，这样它只会在Activity 不为空时改变亮度（在这种情况下it 是Activity）。

class BrightnessFragment : Fragment(), Injectable {

    companion object {
        // Using a constant to make the code cleaner.
        private const val MAX_BRIGHTNESS = 1F
    }

    // Our stored previous brightness.
    private var previousBrightness = MAX_BRIGHTNESS

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)

        (activity as? AppCompatActivity)?.let {
            val attributes = it.window.attributes

            // Store the previous brightness
            previousBrightness = attributes.screenBrightness

            // Set the brightness to MAX_BRIGHTNESS.
            attributes.screenBrightness = MAX_BRIGHTNESS
            it.window.attributes = attributes
        }
    }

    override fun onDestroy() {
        (activity as? AppCompatActivity)?.let {
            val attributes = it.window.attributes

            // Set the brightness to previousBrightness.
            attributes.screenBrightness = previousBrightness
            it.window.attributes = attributes
        }
        // Don't forget to called super.onDestroy()
        super.onDestroy()
    }
}