Fragment监听返回键（Fragment响应Activity的onKeyDown事件）Kotlin版

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/zqd1984309864/article/details/78074451

在Fragment不仅仅只可以监听返回键哦，所有你见过的按键都可以监听，什么A~Z，0~9，F1~F12等等我就不举例子了。至于为什么写这篇博客，因为我的项目是一个Activity+多个Fragment架构的，下面进入正题。。。。直接上代码（原创转载请标明）

    override fun onKeyDown(keyCode: Int, event: KeyEvent?): Boolean {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if (isInterception) {
                if (backListener != null) {
                    backListener!!.onbackForward()
                    return false
                }
            }
        } else if (keyCode == KeyEvent.KEYCODE_STAR) {
            if (startListener != null) {
                startListener!!.onStartButtonPressed()
                return false
            }
        } else if (keyCode == KeyEvent.KEYCODE_POUND) {
            if (poundListener != null) {
                poundListener!!.onPoundButtonPressed()
                return false
            }
        } else if (keyCode == KeyEvent.KEYCODE_PERIOD) {
            if (pointListener != null) {
                pointListener!!.onPointButtonPressed()
                return false
            }
        } else if (keyCode == KeyEvent.KEYCODE_F1) {
            if (f1Listener != null) {
                f1Listener!!.onF1Pressed()
            }
        } else if (keyCode == KeyEvent.KEYCODE_F2) {
            if (f2Listener != null) {
                f2Listener!!.onF2Pressed()
            }
        } else if (keyCode == KeyEvent.KEYCODE_F3) {
            if (f3Listener != null) {
                f3Listener!!.onF3Pressed()
            }
        }
        return super.onKeyDown(keyCode, event)
    }

以上代码是写在MainActivity里面的，在onkeydown事件下监听不同按键的KeyKode（可以参考keycode列表传送门--->http://www.cnblogs.com/bluestorm/p/4886662.html）,我这里主要监听了星号键，井号键，英文.,F1,F2,F3,有人会问为什么要监听F1，F2，F3，因为最近在做PDA，按键比较多。废话不多说，那我们怎么把这个Activity中的事件传到Fragment中呢，就是通过接口，上代码：

interface FragmentF1Listener {
    fun onF1Pressed()
}

这里简单的举了一个例子，我们通过接口回调的方式将事件传到Fragment，所以定义了一个方法，onF1Pressed（），接下来在BaseFragment实现这个接口，从而实现接口的方法onF1Pressed（），并且在fragment中初始化Activity中定义的接口对象，下面是代码：

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        if (activity is MainActivity) {
            (activity as MainActivity).backListener = this
            (activity as MainActivity).startListener = this
            (activity as MainActivity).poundListener = this
            (activity as MainActivity).pointListener = this

            (activity as MainActivity).f1Listener = this
            (activity as MainActivity).f2Listener = this
            (activity as MainActivity).f3Listener = this
//            activity.isInterception = true
        }
    }

记得要在销毁时，消除引用，下面是代码

    override fun onDestroy() {
        super.onDestroy()
        if (activity is MainActivity) {
            (activity as MainActivity).backListener = null
            (activity as MainActivity).startListener = null
            (activity as MainActivity).poundListener = null
            (activity as MainActivity).pointListener = null

            (activity as MainActivity).f1Listener = null
            (activity as MainActivity).f2Listener = null
            (activity as MainActivity).f3Listener = null
//            activity.isInterception = true
        }
        if (presenter != null) {
            presenter!!.onDestroy()
        }
    }

这样就可以实现正在Framgnet中监听Back，以及更多的键了