Android-监听虚拟键盘状态

Android系统本身没有提供监听虚拟键盘的隐藏或显示API，
要实现该功能，我们需要间接来解决，当虚拟键盘显示／隐藏是页面当布局会发生改变，我们可以监听页面的RootView的布局变化来解决该问题：

关键代码如下:

public class TestActivity extends Activity {


    private ViewTreeObserver.OnGlobalLayoutListener mGlobalLayoutListener;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        //create a listener to listen root view layout's status
        mGlobalLayoutListener = new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {

                final Rect r = new Rect();
                //r will be populated with the coordinates of your view that area still visible.
                getWindow().getDecorView().getWindowVisibleDisplayFrame(r);

                int originDecordViewHeight = getWindow().getDecorView().getHeight();
                int visibleDecordViewHeight = r.bottom - r.top;//not include status bar
                final int heightDiff = originDecordViewHeight - visibleDecordViewHeight;

                if (heightDiff > 200) {
                    //当heightDiff大于某个阀值(此处测试方便设为200)可以认为是键盘出现
                    onKeybaordShow();
                } else {
                    //键盘消失
                    onKeybaordHide();
                }
            }


        };

        getWindow().getDecorView().getViewTreeObserver().addOnGlobalLayoutListener(mGlobalLayoutListener);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        //反注册，避免内存泄漏
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            getWindow().getDecorView().getViewTreeObserver().removeOnGlobalLayoutListener(mGlobalLayoutListener);
        }
        mGlobalLayoutListener = null;
    }
}

注意：清单文件中TestActivity 的android:windowSoftInputMode需设置adjustResize，否则键盘显示页面布局不会变化，上述的方法也就失效了