解决：Android Lambda 造成内存泄露

class MyActivity : Activity() {

	override fun onWindowFocusChanged(hasFocus: Boolean) {
        super.onWindowFocusChanged(hasFocus)
        if (hasFocus) {
			// startCheckClipboard 中存在耗时操作
            CommandManager.startCheckClipboard { showCommandOtherTypeDialog() }
        }
    }

    open fun showCommandOtherTypeDialog(){
        CommandManager.showFormulaDialog(supportFragmentManager,true, MtCommandManager.CommandTypeEnum.COMMAND_TYPE_OTHER)
    }
}

object CommandManager : CoroutineScope by WorkScope {
 	fun startCheckClipboard(block: (() -> Unit)? = null) {
		// 耗时任务
		... 
		block.get()?.invoke()
	}
}

问题原因：startCheckClipboard 方法有耗时任务，造成了内存泄露。

class MyActivity : Activity() {

	override fun onWindowFocusChanged(hasFocus: Boolean) {
        super.onWindowFocusChanged(hasFocus)
        if (hasFocus) {
			// startCheckClipboard 中存在耗时操作
            CommandManager.startCheckClipboard { showCommandOtherTypeDialog() }
        }
    }

    open fun showCommandOtherTypeDialog(){
        CommandManager.showFormulaDialog(supportFragmentManager,true, MtCommandManager.CommandTypeEnum.COMMAND_TYPE_OTHER)
    }
}

object CommandManager : CoroutineScope by WorkScope {
 	fun startCheckClipboard(block: (() -> Unit)? = null) {
        // 防止耗时任务造成内存泄露
        val weakBlock: WeakReference<(() -> Unit)?> = WeakReference(block)
		... 
		weakBlock.get()?.invoke()
	}
}

我尝试在做耗时任务的过程中手动执行一次 GC，发现回调就不会执行了，说明这个方案不可行！

为什么会被回收掉呢？

很明显，lambda 方法内的新生代变量，很容易被回收的，如果让 lambda 的生命周期同 Activity 一致就可以了。

我们稍加改动：

class MyActivity : Activity() {

	// 成员变量存储回调，方便耗时任务用弱引用存储 block，避免无法释放造成内存泄露
    private val checkClipboardCallback = { showCommandOtherTypeDialog() }

	override fun onWindowFocusChanged(hasFocus: Boolean) {
        super.onWindowFocusChanged(hasFocus)
        if (hasFocus) {
			// startCheckClipboard 中存在耗时操作
            CommandManager.startCheckClipboard(checkClipboardCallback)
        }
    }

    open fun showCommandOtherTypeDialog(){
        CommandManager.showFormulaDialog(supportFragmentManager,true, MtCommandManager.CommandTypeEnum.COMMAND_TYPE_OTHER)
    }
}

object CommandManager : CoroutineScope by WorkScope {
 	fun startCheckClipboard(block: (() -> Unit)? = null) {
        // 防止耗时任务造成内存泄露
        val weakBlock: WeakReference<(() -> Unit)?> = WeakReference(block)
		... 
		weakBlock.get()?.invoke()
	}
}

搞定！