android.app.Fragment$InstantiationException 解决办法

android.app.Fragment$InstantiationException 解决办法

        在实际的开发中，我遇到过两次android.app.Fragment$InstantiationException报错。

        其中一次报错，根据报错提示 “make sure class name exists, is public, and has an empty constructor that is public” ，若Fragement定义有带参构造函数，则一定要定义public的默认的构造函数。即可解决此问题。如果硬要携带参数进去，可以通过Intent结合Bunble的方式携带进去。 

        第二次报错如下贴的log信息，在“is public, and has an empty constructor that is public” 都满足的情况下，编译ENG版本运行没有任何问题，但是编译USER版本就会出现CRASH错误。原因在于USER版本编译时会代码混淆。

E/AndroidRuntime( 3253): FATAL EXCEPTION: main

E/AndroidRuntime( 3253): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.settings/com.android.settings.SubSettings}: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.android.settings.mcwill.McWiLLSettings: make sure class name exists, is public, and has an empty constructor that is public

E/AndroidRuntime( 3253):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1964) 
E/AndroidRuntime( 3253):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1989) 
E/AndroidRuntime( 3253):     at android.app.ActivityThread.access$600(ActivityThread.java:126) 
E/AndroidRuntime( 3253):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1155) 
E/AndroidRuntime( 3253):     at android.os.Handler.dispatchMessage(Handler.java:99) 
E/AndroidRuntime( 3253):     at android.os.Looper.loop(Looper.java:137) 
E/AndroidRuntime( 3253):     at android.app.ActivityThread.main(ActivityThread.java:4482) 
E/AndroidRuntime( 3253):     at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 3253):     at java.lang.reflect.Method.invoke(Method.java:511) 
E/AndroidRuntime( 3253):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787) 
E/AndroidRuntime( 3253):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554) 
E/AndroidRuntime( 3253):     at dalvik.system.NativeStart.main(Native Method) 
E/AndroidRuntime( 3253): Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.android.settings.mcwill.McWiLLSettings: make sure class name exists, is public, and has an empty constructor that is public 
E/AndroidRuntime( 3253):     at android.app.Fragment.instantiate(Fragment.java:581) 
E/AndroidRuntime( 3253):     at android.preference.PreferenceActivity.switchToHeaderInner(PreferenceActivity.java:1120) 
E/AndroidRuntime( 3253):     at android.preference.PreferenceActivity.switchToHeader(PreferenceActivity.java:1136) 
E/AndroidRuntime( 3253):     at android.preference.PreferenceActivity.onCreate(PreferenceActivity.java:532) 
E/AndroidRuntime( 3253):     at com.android.settings.Settings.onCreate(Settings.java:99) 
E/AndroidRuntime( 3253):     at android.app.Activity.performCreate(Activity.java:4465)
E/AndroidRuntime( 3253):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
E/AndroidRuntime( 3253):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1928) 
E/AndroidRuntime( 3253):     ... 11 more 
E/AndroidRuntime( 3253): Caused by: java.lang.ClassNotFoundException: com.android.settings.mcwill.McWiLLSettings 
E/AndroidRuntime( 3253):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61) 
E/AndroidRuntime( 3253):     at java.lang.ClassLoader.loadClass(ClassLoader.java:501) 
E/AndroidRuntime( 3253):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461) 
E/AndroidRuntime( 3253):     at android.app.Fragment.instantiate(Fragment.java:571) 
E/AndroidRuntime( 3253):     ... 18 more 
W/ActivityManager(  422):   Force finishing activity com.android.settings/.SubSettings 
W/ActivityManager(  422):   Force finishing activity com.android.settings/.Settings 

        解决办法： 

        在对应模块的proguard.flags文件中引入该Fragment所在的类包即可。比如： -keep class com.android.settings.wifi.*Settings