录制音频播放器android中的NullPointerException
日志:录制音频播放器android中的NullPointerException,android,exception,nullpointerexception,android-mediarecorder,Android,Exception,Nullpointerexception,Android Mediarecorder,日志: package com.example.projectlayout; import java.io.File; import android.media.MediaRecorder; import android.os.Bundle; import android.os.Environment; import android.os.SystemClock; import android.app.Activity; import android.content.Intent;
package com.example.projectlayout;
import java.io.File;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Environment;
import android.os.SystemClock;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.Chronometer;
import android.widget.Toast;
public class MainActivity extends Activity {
Chronometer time;
int i=0;
MediaRecorder recorder;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
time=(Chronometer)findViewById(R.id.chronometer1);
String name="myrecord"+i++;
File sdcard=Environment.getExternalStorageDirectory();
System.out.println(sdcard.toString());
File recording=new File(sdcard,"videoRecordingFileZ");
if(!recording.exists())
{
System.out.println("inside if");
recording.mkdir();
}
String rec=recording.getAbsolutePath()+"/Record"+".3GP";
try{
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
recorder.setOutputFile(rec);
recorder.prepare();
}
catch(Exception e){
System.out.println(e);
recorder.start();
}}
public void startrecording(View v)
{
Toast.makeText(MainActivity.this, "START RECORDING", Toast.LENGTH_LONG).show();
time.setBase(SystemClock.elapsedRealtime());
time.start();
}
public void stoprecording(View v)
{
Toast.makeText(MainActivity.this, "STOP RECORDING", Toast.LENGTH_LONG).show();
time.stop();
}
public void showrecording(View v)
{
Toast.makeText(MainActivity.this, "Show RECORDING", Toast.LENGTH_LONG).show();
Intent i=new Intent(MainActivity.this,Showlist.class);
startActivity(i);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}}
如果希望获得异常的帮助,您确实需要提供完整的错误消息和调用堆栈 话虽如此,我可以看出您的代码中存在问题(假设您提供了所有相关部分)
从未为“recorder”成员变量赋值,但在onCreate()的try和catch子句中取消了对该变量的引用。可能是catch子句中的取消引用导致了NullPointerException。您没有初始化MediaRecorder:
03-27 00:49:22.224: E/AndroidRuntime(470): FATAL EXCEPTION: main
03-27 00:49:22.224: E/AndroidRuntime(470): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.projectlayout/com.example.projectlayout.MainActivity}: java.lang.NullPointerException
03-27 00:49:22.224: E/AndroidRuntime(470): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.projectlayout/com.example.projectlayout.MainActivity}: java.lang.NullPointerException
您应该在onCreate方法中执行此操作:
MediaRecorder recorder;
在使用记录器之前
或收到NullPointerException
顺便说一句:改进代码缩进(在EclipseCtrl+Ikeybord快捷方式中)以提高代码的可读性
关于下一个问题:
IllegalStateException
:
查看android文档中的:
以及提供的示例代码:
recorder = new MediaRecorder();
@user3465656:我删除了您添加到我的答案中的堆栈跟踪,因为它属于您的问题,而不是建议的答案之一。还请注意,您指定的编辑答案的原因不会显示为该答案下的注释(出于某些原因)。我是新用户,因此我面临此网站如何使用的问题,,,抱歉mistake@user3465656我明白了。此外,您插入的堆栈跟踪没有显示NullPointerException——这是整个堆栈跟踪,还是您更改了代码?请根据需要修改您的问题。现在它的工作问题在这一行,我不想添加这一行记录器。start();recorder.start();记录器。释放();如果此问题已回答,但您有一个新的后续问题,请提交一个新问题。请记住包括相关的堆栈跟踪。好!你介意点击这个答案旁边的接受按钮吗?这就是我们在stackoverflow将问题标记为已解决的方式。我指的是
✔代码>检查图标,它在我答案的左上角。同时检查
MediaRecorder recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
recorder.setOutputFile(PATH_NAME);
recorder.prepare();
recorder.start(); // Recording is now started
...
recorder.stop();
recorder.reset(); // You can reuse the object by going back to setAudioSource() step
recorder.release(); // Now the object cannot be reused