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我有以下片段。它工作得很好，直到我旋转我的设备。RadarSelectionFragment然后它会因失败而崩溃Instantiate。FragmentPagerAdapter和有问题的代码Fragment如下：

@SuppressLint("DefaultLocale")
public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter() {
           // Do some stuff     
    }


    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        if (position == 0) {
            Fragment fragment = new RadarSelectionFragment();
            Bundle args = new Bundle();
            args.putInt(RadarSelectionFragment.ARG_SECTION_NUMBER, position + 1);
            fragment.setArguments(args);
            return fragment;
        } else if (position == 1) {
            Fragment fragment = new WeatherMapDisplayFragment();
            Bundle args = new Bundle();
            args.putInt(WeatherMapDisplayFragment.ARG_SECTION_NUMBER, position + 1);
            fragment.setArguments(args);
            return fragment;
        } else {
            Fragment tf = new RadarSelectionFragment();
            return tf;
        }
    }

    @Override
    public int getCount() {
        return 2;
    }

    @SuppressLint("DefaultLocale")
    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
        case 0:
            return getString(R.string.title_section1).toUpperCase();
        case 1:
            return getString(R.string.title_section2).toUpperCase();
        }
        return null;
    }
}


public static class RadarSelectionFragment extends Fragment {

    public static final String ARG_SECTION_NUMBER = "section_number";

    public RadarSelectionFragment() {}

    @Override
    public final View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (getArguments().getInt(ARG_SECTION_NUMBER) == 1) {
            return inflater.inflate(R.layout.radars, container, false);
        } else {
            return container;
        }

    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

     @Override
     public void onSaveInstanceState(Bundle outState) {

         super.onSaveInstanceState(outState);
     }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setRetainInstance(true);

        ...
    }

    public void onNothingSelected(AdapterView<?> parent) {
                // Another interface callback
            }
        });
    }


} 

public class WeatherMapDisplayFragment extends Fragment {

    public static final String ARG_SECTION_NUMBER = "section_number";

    public WeatherMapDisplayFragment() {
    }

    @Override
    public final View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (getArguments().getInt(ARG_SECTION_NUMBER) == 2) {
            return inflater.inflate(R.layout.display, container, false);
        } else {
            return container;
        }
    }
}

我试过用谷歌搜索这个问题，但我一直在寻找各种与确保问题相关的解决方案Fragment Class（static我已经完成了）。

我对 Android 编程比较陌生，所以如果您回答，如果您有时间，能否请您发布一个示例和/或链接到其他示例。

提前致谢！

编辑 1：堆栈跟踪

01-21 13:46:31.907: E/AndroidRuntime(1101): FATAL EXCEPTION: main
01-21 13:46:31.907: E/AndroidRuntime(1101): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.radarau/com.example.radarau.MainActivity}: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.radarau.MainActivity$WeatherMapDisplayFragment: make sure class name exists, is public, and has an empty constructor that is public
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3692)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.access$700(ActivityThread.java:141)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1240)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.os.Looper.loop(Looper.java:137)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.main(ActivityThread.java:5039)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at java.lang.reflect.Method.invokeNative(Native Method)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at java.lang.reflect.Method.invoke(Method.java:511)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at dalvik.system.NativeStart.main(Native Method)
01-21 13:46:31.907: E/AndroidRuntime(1101): Caused by: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.radarau.MainActivity$WeatherMapDisplayFragment: make sure class name exists, is public, and has an empty constructor that is public
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.support.v4.app.Fragment.instantiate(Fragment.java:405)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.support.v4.app.FragmentState.instantiate(Fragment.java:97)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.support.v4.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1767)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:208)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at com.example.radarau.MainActivity.onCreate(MainActivity.java:35)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.Activity.performCreate(Activity.java:5104)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
01-21 13:46:31.907: E/AndroidRuntime(1101):     ... 12 more
01-21 13:46:31.907: E/AndroidRuntime(1101): Caused by: java.lang.InstantiationException: can't instantiate class com.example.radarau.MainActivity$WeatherMapDisplayFragment; no empty constructor
01-21 13:46:31.907: E/AndroidRuntime(1101):     at java.lang.Class.newInstanceImpl(Native Method)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at java.lang.Class.newInstance(Class.java:1319)
01-21 13:46:31.907: E/AndroidRuntime(1101):     at android.support.v4.app.Fragment.instantiate(Fragment.java:394)
01-21 13:46:31.907: E/AndroidRuntime(1101):     ... 19 more
4

1 回答 1

1

你的日志猫说

Caused by: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.radarau.MainActivity$WeatherMapDisplayFragment: make sure class name exists, is public, and has an empty constructor that is public

您应该为此提供一个公共默认构造函数

public WeatherMapDisplayFragment() {
   // Do some stuff     
}

如果该类是嵌套的，则将其class设置为static class并提供公共默认构造函数或将该片段移动到新的 java 文件中。

于 2013-01-21T03:49:04.967 回答