Android-为什么GC突然删除了我的对象？

Question

When I'm creating object to write to output stream (size is lower than 150KB) it probably gets instantly destroyed, because of:

System.out.println("Sending object..");
Packet p = new Packet(mJpegData); // here exists
System.out.println(p); // reference exists
oos.writeObject(p); // null exception error

full error:

04-26 21:37:01.414: W/System.err(12888): java.lang.NullPointerException
04-26 21:37:01.414: W/System.err(12888):    at pl.aadamczyk.webcamera.Preview$PreCallback.onPreviewFrame(Preview.java:148)
04-26 21:37:01.417: W/System.err(12888):    at android.hardware.Camera$EventHandler.handleMessage(Camera.java:583)
04-26 21:37:01.417: W/System.err(12888):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-26 21:37:01.417: W/System.err(12888):    at android.os.Looper.loop(Looper.java:130)
04-26 21:37:01.417: W/System.err(12888):    at android.app.ActivityThread.main(ActivityThread.java:3687)
04-26 21:37:01.417: W/System.err(12888):    at java.lang.reflect.Method.invokeNative(Native Method)
04-26 21:37:01.417: W/System.err(12888):    at java.lang.reflect.Method.invoke(Method.java:507)
04-26 21:37:01.417: W/System.err(12888):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
04-26 21:37:01.417: W/System.err(12888):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
04-26 21:37:01.417: W/System.err(12888):    at dalvik.system.NativeStart.main(Native Method)
04-26 21:37:01.472: D/dalvikvm(12888): GC_FOR_MALLOC freed 1152K, 57% free 2820K/6535K, external 1596K/2108K, paused 17ms
04-26 21:37:01.472: I/System.out(12888): My Object has been GC'd. Packet@4063d908
04-26 21:37:01.523: D/dalvikvm(12888): GC_CONCURRENT freed 28K, 50% free 3311K/6535K, external 1596K/2108K, paused 3ms+10ms

"My Object has been GC'd. " is printed by Packet's finalizer.

whole code: http://pastebin.com/zc5TcSgY

Why GS is removing my object? I've got in about 120 MB free memory.

How to fix it?

Answer 1

I think the problem is with oos because it might be the one causing NullPointerException .

Change your code a little as below:

System.out.println("Sending object..");
Packet p = new Packet(mJpegData); // here exists
System.out.println(p); // reference exists 

if(oos != null)
    oos.writeObject(p);
else
    Log.w("oos", "its null");