问题
I'm trying to make an app that starts recording when a button is clicked, and when is clicked again it stops recording. I don't think I have problems when I'm recording, but when I click the button again the application crashes with NullPointerException and it is said that stop is called in invalid state 1
My code:
package com.example.victwo;
import java.io.IOException;
import android.media.MediaRecorder;
public class Audio {
private String path;
MediaRecorder myAudioRecorder = null;
public Audio(String path) {
this.path = path;
}
public void play() {
}
public void startRecording() {
myAudioRecorder = new MediaRecorder();
myAudioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
myAudioRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
myAudioRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
myAudioRecorder.setOutputFile(path);
try {
myAudioRecorder.prepare();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
myAudioRecorder.start();
}
public void stopRecording() {
myAudioRecorder.stop();
myAudioRecorder.release();
myAudioRecorder = null;
}
}
This is the code from the activity where I call the Audio Class methods:
case R.id.action_record:
Audio recAndPlay = new Audio(this.path + "/" + this.title);
if(flag == 0) {
Log.d("RECORD", "START");
flag = 1;
if(title.equals("")) {
setTitle();
}
recAndPlay.startRecording();
return true;
}
if(flag == 1) {
Log.d("RECORD", "STOP");
recAndPlay.stopRecording();
}
return true;
The logcat:
04-05 14:02:58.909: E/AndroidRuntime(5730): FATAL EXCEPTION: main
04-05 14:02:58.909: E/AndroidRuntime(5730): java.lang.NullPointerException
04-05 14:02:58.909: E/AndroidRuntime(5730): at com.example.victwo.Audio.stopRecording(Audio.java:41)
04-05 14:02:58.909: E/AndroidRuntime(5730): at com.example.victwo.NoteActivity.onOptionsItemSelected(NoteActivity.java:158)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.app.Activity.onMenuItemSelected(Activity.java:2205)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:372)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.app.ActionBarActivity.superOnMenuItemSelected(ActionBarActivity.java:244)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.app.ActionBarActivityDelegateBase.onMenuItemSelected(ActionBarActivityDelegateBase.java:339)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.app.ActionBarActivity.onMenuItemSelected(ActionBarActivity.java:130)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.app.ActionBarActivityDelegateBase.onMenuItemSelected(ActionBarActivityDelegateBase.java:344)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:777)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:158)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:922)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:544)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.support.v7.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:105)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.view.View.performClick(View.java:2485)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.view.View$PerformClick.run(View.java:9080)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.os.Handler.handleCallback(Handler.java:587)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.os.Handler.dispatchMessage(Handler.java:92)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.os.Looper.loop(Looper.java:123)
04-05 14:02:58.909: E/AndroidRuntime(5730): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-05 14:02:58.909: E/AndroidRuntime(5730): at java.lang.reflect.Method.invokeNative(Native Method)
04-05 14:02:58.909: E/AndroidRuntime(5730): at java.lang.reflect.Method.invoke(Method.java:507)
04-05 14:02:58.909: E/AndroidRuntime(5730): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-05 14:02:58.909: E/AndroidRuntime(5730): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-05 14:02:58.909: E/AndroidRuntime(5730): at dalvik.system.NativeStart.main(Native Method)
回答1:
Initialize your media player in out side of startRecording()
myAudioRecorder = new MediaRecorder();
Modify your code like following
public class Audio {
private String path;
MediaRecorder myAudioRecorder = new MediaRecorder();
public Audio(String path) {
this.path = path;
}
public void play() {
}
public void startRecording() {
myAudioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
myAudioRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
myAudioRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
myAudioRecorder.setOutputFile(path);
try {
myAudioRecorder.prepare();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
myAudioRecorder.start();
}
public void stopRecording() {
myAudioRecorder.stop();
myAudioRecorder.release();
myAudioRecorder = null;
}
}
Hope this will help you
回答2:
The myAudioRecorder must be null at the time you call stopRecording(). I can not judge from your code why (do you call stopRecording() twice?). If you post more code I might be able to help you. You could also surround the statements in the stopRecording()method with a check:
public void stopRecording() {
if(myAudioRecorder != null){
myAudioRecorder.stop();
myAudioRecorder.release();
myAudioRecorder = null;
}
}
回答3:
private void stopRecording() {
if (null != recorder) {
recorder.stop();
recorder.reset();
recorder.release();
recorder = null;
}
}
回答4:
please check if MediaRecorder object is not null before stopping it.
回答5:
I don't think you are taking the right approach. why declare media player as null in the beginning. initialise in first and when done use methods of media player class to release/reset it.
also before you start using mediaplayer use if(){...}block to check whether it is initialised. example below;
private void stopRecording() {
if (myAudioRecorder != null) {
myAudioRecorder.stop();
myAudioRecorder.reset();
myAudioRecorder.release();
myAudioRecorder = null;
}
}
回答6:
Another reason could be, that it was already stopped, and then you are re-using .stop() function, which causes problems, check your logic and code...
来源：https://stackoverflow.com/questions/22880037/nullpointerexception-when-recording-is-stopped-android