Android APP检测实体按键事件详解

package com.example.keyeventdemo;
 
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.KeyEvent;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
    private TextView key_result;
    private String desc = "";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        key_result = (TextView) findViewById(R.id.key_result);
    }
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        key_result = (TextView) findViewById(R.id.key_result);
    }
 
   @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        desc = String.format("%sphysical key coce is %d", desc, keyCode);
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            desc = String.format("%s, KEYCODE_BACK", desc);
        } else if (keyCode == KeyEvent.KEYCODE_MENU) {
            desc = String.format("%s, KEYCODE_MENU", desc);
        } else if (keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
            desc = String.format("%s, KEYCODE_VOLUME_UP", desc);
        } else if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
            desc = String.format("%s, KEYCODE_VOLUME_DOWN", desc);
        }else  {
            desc = String.format("%s, KEYCODE_VOLUME is unknown", desc);
        }
        desc = desc + "\n";
        key_result.setText(desc);
        //返回true表示不再响应系统动作，返回false表示继续响应系统动作
        return true;
      // return  false;
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="5dp">
 
    <TextView
        android:id="@+id/tv_hard"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:gravity="center"
        android:text="please press the physics button"
        android:textSize="16sp" />
 
    <TextView
        android:id="@+id/key_result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="16sp" />
 
</LinearLayout>