背景

先说下需求，大意就是点击某个EditText后，系统输入法弹起。此时我们要在键盘上方展示一个视图。为了方便演示，我们这里就在键盘上方弹出一个Toast。

分析

我们可以把事情分为几个步骤：

1. 监听到键盘弹起；
2. 获取键盘高度H；
3. 在高度H处展示视图；

代码

先看效果

450ac51275c533f2.gif

先定义一个接口，给键盘弹起事件增加一个接口。

interface IKeyBoardVisibleListener {
    fun onSoftKeyBoardVisible(visible: Boolean?, keyboardHeight: Int?)
}

为了方便演示，我们在Activity的onResume方法中直接注册了这个监听。

open class MainActivity: Activity(){

    private var mRootView:RelativeLayout?=null
    private var mEditText: EditText? = null


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        initViews()
    }

    private fun initViews() {
        mRootView = this.findViewById(R.id.root)
        mEditText = findViewById(R.id.editText)
    }


    override fun onResume() {
        super.onResume()
        this.addOnSoftKeyBoardVisibleListener(this, object:IKeyBoardVisibleListener{
            override fun onSoftKeyBoardVisible(visible: Boolean?, keyboardHeight: Int?) {
                var toastText:String = "";
                if (keyboardHeight == getStatusBarHeight()) {
                    toastText = "居底显示"
                } else {
                    toastText = "键盘上方显示"
                }
                val toast = Toast.makeText(this@MainActivity, toastText, Toast.LENGTH_LONG)
                toast.setGravity(Gravity.BOTTOM, 0, keyboardHeight!!)
                toast.show()
                //Log.d("MyLog","软键盘可见：" + visible + ",键盘高度:" + keyboardHeight)
            }
        })
    }
    private fun getStatusBarHeight():Int {
        val wm:WindowManager = this.getSystemService(Context.WINDOW_SERVICE) as WindowManager
        val point = Point()
        wm.defaultDisplay.getSize(point)
        val width = point.x
        val height = point.y
        var result = 0
        val resourceId = this.getResources().getIdentifier("status_bar_height", "dimen", "android")
        if (resourceId > 0) {
            result = this.getResources().getDimensionPixelSize(resourceId)
        }
        return result;
    }



    open fun addOnSoftKeyBoardVisibleListener(activity: Activity?, listener: IKeyBoardVisibleListener? ) {
        var decorView: View? = activity?.getWindow()?.getDecorView();
        decorView?.getViewTreeObserver()?.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
            @Override
            override fun onGlobalLayout() {

                var rect: Rect = Rect();
                decorView?.getWindowVisibleDisplayFrame(rect);
                //计算出可见屏幕的高度
                var displayHight: Int? = rect.bottom - rect.top;
                //获得屏幕整体的高度
                var hight: Int? = decorView.getHeight();
                //获得键盘高度
                var keyboardHeight: Int? = hight!! - displayHight!!
               //如果新的可见高度小于一定比例了，我们就认为键盘已经弹起
                var visible: Boolean? = (displayHight / hight) < 0.8
                listener?.onSoftKeyBoardVisible(visible, keyboardHeight)

            }
        });
    }
}

参考

当然，上面的代码很分散。这个方法也并非原创，生产开发可以参考这篇文章的封装。
https://www.jianshu.com/p/9bba256f261f