ndroid.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment benguo.simphon

android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment benguo.simphone.payy.view.ContentFragment: make sure class name exists, is public, and has an empty constructor that is public  解决办法

     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。

写一个静态方法来实例化自己的Fragment。代码如下：

public static final Fragment newInstance(String key){         Fragment fragment = new RealtimeSearchFragment();  

       Bundle bundle = new Bundle();  

        bundle.putString("key", key);  

        fragment.setArguments(bundle);  

        return fragment;  

    }  

在自己的Activity里这样获取这个Fragment：

1. Fragment realtimeSearchFragment = RealtimeSearchFragment.newInstance(realSearchKey);  

在自己的Fragment 的onCreateView方法里获取Activity传过来的值：

1. getArguments().getString("key") 
   

  还有一种报错如下贴的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