Why does the start() method of MediaRecorder throw an IllegalStateException?

问题

I am trying to record audio but the start() method of MediaRecorder class throws an IllegalStateException. I use the following code:

MediaRecorder recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
recorder.setOutputFile("/sdcard/");
try {
    recorder.prepare();
} catch (IllegalStateException e) {

// TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
Log.i("Try","Exception");
recorder.start(); 

And following permission

<uses-permission android:name="android.permission.RECORD_AUDIO" />

回答1:

Vijay, recorder.setOutputFile("/sdcard/"); is setting a directory, not a file. Replace that with:

mFileName = Environment.getExternalStorageDirectory().getAbsolutePath();
mFileName += "/youraudiofile.3gp";

Using "/sdcard" hard codes a path which is fragile, so use the above

Also, for this to work you must add

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

to your AndroidManifext.xml

回答2:

It may be helpful for some one in future. IllegalstateException is thrown when the MediaRecorder. Prepare method is not called or called after Mediarecorder.start or before configuring audio/video sources,format and encoders. The correct order of configuration mentioned in camera developer guide on android documentation

1. camera unlock
2. control of camera to media recorder -> setCamera
3. set audio/video source, format,encoder
4. prepare
5. start

来源：https://stackoverflow.com/questions/5177039/why-does-the-start-method-of-mediarecorder-throw-an-illegalstateexception