我这个基于回调的事件处理函数怎么没反应呢

Android studio 的 Android Monitor 窗口没有输出。另外 Log 类的 e函数、d函数、i函数、v函数有什么区别

<LinearLayout

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical">



    <com.example.administrator.third.MyButton

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:text="单击我"/>

</LinearLayout>

package com.example.administrator.third;



import android.app.Activity;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Paint;

import android.os.Handler;

import android.os.Message;

import android.provider.MediaStore;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.AttributeSet;

import android.util.DisplayMetrics;

import android.util.Log;

import android.view.Display;

import android.view.KeyEvent;

import android.view.View;

import android.view.Window;

import android.view.WindowManager;

import android.widget.AdapterView;

import android.widget.ArrayAdapter;

import android.widget.AutoCompleteTextView;

import android.widget.Button;

import android.widget.CheckBox;

import android.widget.CompoundButton;

import android.widget.EditText;

import android.widget.GridView;

import android.widget.ImageView;

import android.widget.MultiAutoCompleteTextView;

import android.widget.ProgressBar;

import android.widget.RadioGroup;

import android.widget.SimpleAdapter;

import android.widget.ToggleButton;



import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Objects;



public class MainActivity extends Activity

{

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

    }

}



class MyButton extends Button

{

    public MyButton(Context context, AttributeSet set)

    {

        super(context, set);

    }

    public boolean onKeyDown(int keyCode, KeyEvent event)

    {

        super.onKeyDown(keyCode, event);

        Log.e("eeee", "the onKeyDown in MyButton   eeeeeeeeee");

        Log.i("eeee", "the onKeyDown in MyButton   iiiiiiiiii");

        Log.v("eeee", "the onKeyDown in MyButton   vvvvvvvvvv");

        return true;

    }

}