setParameters异常…无法使用Camera

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    isPreviewRunning = false;
    surface = (SurfaceView)findViewById(R.id.surface);
    holder = surface.getHolder();
  holder.addCallback(this);


}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
    if (isPreviewRunning) {  
          camera.stopPreview();  
         }  

     Camera.Parameters p = camera.getParameters();  
     p.setPreviewSize(480, 800);  
     p.setPictureFormat(PixelFormat.JPEG);
     camera.setParameters(p); 

     try {
        camera.setPreviewDisplay(holder);

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }  
     camera.startPreview();  
     isPreviewRunning=true;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
    // TODO Auto-generated method stub
     camera = Camera.open();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    // TODO Auto-generated method stub
    camera.stopPreview();
    camera.release();
    camera=null;
}

04-13 15:21:36.979: ERROR/AndroidRuntime(14583): FATAL EXCEPTION: main
04-13 15:21:36.979: ERROR/AndroidRuntime(14583): java.lang.RuntimeException: setParameters failed
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.hardware.Camera.native_setParameters(Native Method)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.hardware.Camera.setParameters(Camera.java:655)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at org.mycamera.mycamera.surfaceChanged(mycamera.java:44)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.SurfaceView.updateWindow(SurfaceView.java:546)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.SurfaceView.dispatchDraw(SurfaceView.java:339)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.View.draw(View.java:6742)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.drawChild(ViewGroup.java:1648)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1375)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.View.draw(View.java:6742)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1872)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewRoot.draw(ViewRoot.java:1422)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1167)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1744)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.os.Looper.loop(Looper.java:144)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at android.app.ActivityThread.main(ActivityThread.java:4937)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at java.lang.reflect.Method.invokeNative(Native Method)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at java.lang.reflect.Method.invoke(Method.java:521)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-13 15:21:36.979: ERROR/AndroidRuntime(14583):     at dalvik.system.NativeStart.main(Native Method)