代码：
activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="增加音量时显示提示信息" android:textColor="@android:color/black" android:textSize="25dp" /> </LinearLayout> MainActivity.java
package com.example.volumeup; import android.app.Activity; import android.os.Bundle; import android.view.KeyEvent; import android.view.Menu; import android.view.MenuItem; import android.widget.Toast; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { // TODO Auto-generated method stub if(keyCode==KeyEvent.KEYCODE_VOLUME_UP){ Toast.makeText(this, "音量增加", Toast.LENGTH_LONG).show(); return false; } return super.onKeyDown(keyCode, event); } } 截图：
