android 监听软键盘的弹出和收起

public class MainActivity extends Activity implements OnLayoutChangeListener{         //Activity最外层的Layout视图    private View activityRootView;    //屏幕高度    private int screenHeight = 0;    //软件盘弹起后所占高度阀值    private int keyHeight = 0;         @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);         activityRootView = findViewById(R.id.root_layout);        //获取屏幕高度        screenHeight = this.getWindowManager().getDefaultDisplay().getHeight();        //阀值设置为屏幕高度的1/3        keyHeight = screenHeight/3;    }         @Override    protected void onResume() {        super.onResume();                 //添加layout大小发生改变监听器        activityRootView.addOnLayoutChangeListener(this);    }         @Override    public void onLayoutChange(View v, int left, int top, int right,            int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {                 //old是改变前的左上右下坐标点值，没有old的是改变后的左上右下坐标点值         //      System.out.println(oldLeft +   + oldTop +  + oldRight +   + oldBottom);//      System.out.println(left +   + top +  + right +   + bottom);                          //现在认为只要控件将Activity向上推的高度超过了1/3屏幕高，就认为软键盘弹起        if(oldBottom != 0 && bottom != 0 &&(oldBottom - bottom > keyHeight)){                         Toast.makeText(MainActivity.this, 监听到软键盘弹起..., Toast.LENGTH_SHORT).show();                 }else if(oldBottom != 0 && bottom != 0 &&(bottom - oldBottom > keyHeight)){                         Toast.makeText(MainActivity.this, 监听到软件盘关闭..., Toast.LENGTH_SHORT).show();                 }             }