修改Activity響應音量修飾鍵修改的音頻流

轉自：http://rainhomepage.appspot.com/2010/05/hardware-volume-controls-audio-stream-setvolumecontrolstream

當開發多媒體應用或者遊戲應用的時候，需要使用音量修飾鍵來設定程式的音量大小。在Android系統中有多中音頻流，通過Activity中的函數 setVolumeControlStream(int streamType)可以設定該Activity中音量修飾鍵控制的音頻流，一般在onCreate函數中設定。

Android中有如 下幾種音頻流：

• AudioManager.STREAM_MUSIC  /** The audio stream for music playback */
• AudioManager.STREAM_RING /** The audio stream for the phone ring */
• AudioManager.STREAM_ALARM  /** The audio stream for alarms */
• AudioManager.STREAM_NOTIFICATION /** The audio stream for notifications */
• AudioManager.STREAM_SYSTEM  /** The audio stream for system sounds */
• AudioManager.STREAM_VOICECALL /** The audio stream for phone calls */

setVolumeControlStream函數描述：

void android.app.Activity .setVolumeControlStream(int streamType)

Suggests an audio stream whose volume should be changed by the hardware volume controls.

The suggested audio stream will be tied to the window of this Activity. If the Activity is switched, the stream set here is no longer the suggested stream. The client does not need to save and restore the old suggested stream value in onPause and onResume.

Parameters:

streamType The type of the audio stream whose volume should be changed by the hardware volume controls. It is not guaranteed that the hardware volume controls will always change this stream's volume (for example, if a call is in progress, its stream's volume may be changed instead). To reset back to the default, use  AudioManager.USE_DEFAULT_STREAM_TYPE .