通话记录？

Question

我制作了一个自动呼叫记录器。

我使用媒体记录器

但是当我回复时，我收到一个错误：java.lang.RuntimeException：start failed。

应用程序崩溃，在文件夹中创建文件（3-6kb），但它是空的

所有权限均在

上

代码：

public class CallReceiver extends BroadcastReceiver  {
private MediaRecorder rec;
private boolean recordstarted;
private File file;
String path="/sdcard/alarms";
@Override
public void onReceive(final Context context, Intent intent) {
    TelephonyManager telephonyManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
    file = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_ALARMS);
    rec = new MediaRecorder();
    rec.setAudioSource(MediaRecorder.AudioSource.MIC);
    rec.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    rec.setOutputFile(file.getAbsolutePath()+"/"+"rec.3gp");
    rec.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

    final PhoneStateListener listener = new PhoneStateListener(){
        @Override
        public void onCallStateChanged(int state, String incomingNumber) {
            //mContext = context;
            switch (state)
            {
                case TelephonyManager.CALL_STATE_IDLE:
                    rec.stop();
                    rec.reset();
                    rec.release();
                    recordstarted=false;
                    break;
                case TelephonyManager.CALL_STATE_OFFHOOK:
                    try {
                        rec.prepare();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    rec.start();
                    recordstarted=true;
                case TelephonyManager.CALL_STATE_RINGING:
             autoPickCall(context);

                    break;
            }

        }
    };
    telephonyManager.listen(listener, PhoneStateListener.LISTEN_CALL_STATE);
}

例外：

02-27 10:47:04.101 2312-2312/com.phonedialer.phonedialer E/AndroidRuntime: FATAL EXCEPTION: main
                                                                       Process: com.phonedialer.phonedialer, PID: 2312
                                                                       java.lang.RuntimeException: start failed.
                                                                           at android.media.MediaRecorder.start(Native Method)
                                                                           at com.test.myapplication.CallReceiver$1.onCallStateChanged(CallReceiver.java:63)
                                                                           at android.telephony.PhoneStateListener$1.handleMessage(PhoneStateListener.java:293)
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                           at android.os.Looper.loop(Looper.java:135)
                                                                           at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                                           at java.lang.reflect.Method.invoke(Native Method)
                                                                           at java.lang.reflect.Method.invoke(Method.java:372)
                                                                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)