安卓不允许你在通话过程中修改输出音频流。即使呼叫处于保持状态，它仍然被认为正在进行的通话。你能做的***是玩任何你想要在扬声器并希望麦克风选了。

Android does not allow you to modify the outgoing audio stream during a call. Even though the call is on hold, it is still considered an ongoing call. The best you can do is to play whatever you want to over the loudspeaker and hope the microphone picks it up.