package apk by ant debug failed

when i use cocos2d-x 2.14 create an android project. first time package apk success. but when i package apk second time. it failed when excute command ant debug. The content of error message is:
找不到符号
Buildfile: D:2d-x-2.1.4\projects\fg\proj.android\build.xml

~~set-mode-check:
~~set-debug-files:

~~check-env:
Android SDK Tools Revision 22.0.5
Installed at D:~~bundle-windows-x86-20130729\sdk

~~setup:
Project Name: fg
Project Type: Application
~~set-debug-mode:

~~debug-obfuscation-check:
~~pre-build:

build-setup:
Using latest Build Tools: 18.0.1
Resolving Build Target for fg…
Project Target: Android 2.2
API level: 8
———

[echo] Creating output directories if needed…
[echo] ———-
[echo] Resolving Dependencies for fg…
[dependency] Library dependencies:
[dependency] No Libraries
[dependency]
[dependency] ——————
[dependency] API<=15: Adding annotations.jar to the classpath.
[echo] ———-
[echo] Building Libraries with ‘debug’…
[subant] No sub-builds to iterate on

code-gen:
Found Deleted Target File
Merging AndroidManifest files into one.
Manifest merger disabled. Using project manifest only.
Handling aidl files…
No AIDL files to compile.
———

[echo] Handling RenderScript files…
[renderscript] No RenderScript files to compile.
[echo] ———-
[echo] Handling Resources…
[aapt] Found Deleted Target File
[aapt] Generating resource IDs…
[echo] ———-
[echo] Handling BuildConfig class…
[buildconfig] Generating BuildConfig class.

~~pre-compile:
~~compile:
[javac] Compiling 3 source files to D:2d-x-2.1.4\projects\fg\proj.android\bin\classes
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:26: 错误: 程序包org.cocos2dx.lib不存在
[javac] import org.cocos2dx.lib.Cocos2dxActivity;
[javac] ^
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:27: 错误: 程序包org.cocos2dx.lib不存在
[javac] import org.cocos2dx.lib.Cocos2dxGLSurfaceView;
[javac] ^
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:31: 错误: 找不到符号
[javac] public class fg extends Cocos2dxActivity{
[javac] ^
[javac] 符号: 类 Cocos2dxActivity
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:37: 错误: 找不到符号
[javac] public Cocos2dxGLSurfaceView onCreateView() {
[javac] ^
[javac] 符号: 类 Cocos2dxGLSurfaceView
[javac] 位置: 类 fg
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:34: 错误: 找不到符号
[javac] super.onCreate(savedInstanceState);
[javac] ^
[javac] 符号: 变量 super
[javac] 位置: 类 fg
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:38: 错误: 找不到符号
[javac] Cocos2dxGLSurfaceView glSurfaceView = new Cocos2dxGLSurfaceView(this);
[javac] ^
[javac] 符号: 类 Cocos2dxGLSurfaceView
[javac] 位置: 类 fg
[javac] D:2d-x-2.1.4\projects\fg\proj.android\src\com\fl\fg\fg.java:38: 错误: 找不到符号
[javac] Cocos2dxGLSurfaceView glSurfaceView = new Cocos2dxGLSurfaceView(this);
[javac] ^
[javac] 符号: 类 Cocos2dxGLSurfaceView
[javac] 位置: 类 fg
[javac] 7 个错误

the chinese above means
package org.cocos2dx.lib not exists
can not find symbol public class fg extends Cocos2dxActivity{

why when excute ant debug success at first time. but failed every time later.