您好,我在使用pageViwer和Adapter滑过3个片段时遇到此错误。
这是我的pageAdapter
public class FreedomPageAdapter extends FragmentPagerAdapter {
private List<Fragment> listFragment;
public FreedomPageAdapter(FragmentManager fm, List<Fragment> listFragment) {
super(fm);
this.listFragment = listFragment;
}
/*
* (non-Javadoc)
*
* @see android.support.v4.app.FragmentPagerAdapter#getItem(int)
*/
@Override
public Fragment getItem(int position) {
// TODO Auto-generated method stub
return listFragment.get(position);
}
/*
* (non-Javadoc)
*
* @see android.support.v4.view.PagerAdapter#getCount()
*/
@Override
public int getCount() {
// TODO Auto-generated method stub
return listFragment.size();
}
这是我如何定义网页浏览
viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setOnPageChangeListener(this);
savedListFragment = new SubscribedFragment();
fragmentList.add(savedListFragment);
fragmentList.add(savedListFragment);
fragmentList.add(savedListFragment);
viewPager.setAdapter(new FreedomPageAdapter(fragmentManager(),
fragmentList));
private FragmentManager fragmentManager() {
return getSupportFragmentManager();
}
private FragmentTransaction getFragmentTransaction() {
return fragmentManager().beginTransaction();
}
页面视图监听器
/*
* (non-Javadoc)
*
* @see android.support.v4.view.ViewPager.OnPageChangeListener#
* onPageScrollStateChanged(int)
*/
@Override
public void onPageScrollStateChanged(int arg0) {
}
/*
* (non-Javadoc)
*
* @see
* android.support.v4.view.ViewPager.OnPageChangeListener#onPageScrolled
* (int, float, int)
*/
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
/*
* (non-Javadoc)
*
* @see
* android.support.v4.view.ViewPager.OnPageChangeListener#onPageSelected
* (int)
*/
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
自定义片段对象
public class SubscribedFragment extends Fragment{
/* (non-Javadoc)
* @see android.app.Fragment#onCreate(android.os.Bundle)
*/
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
}
/* (non-Javadoc)
* @see android.app.Fragment#onCreateView(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle)
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
return inflater.inflate(R.layout.discussion_list_layout, container);
}
}
错误的完整堆栈跟踪:
05-02 19:15:44.599: E/AndroidRuntime(19839): FATAL EXCEPTION: main
05-02 19:15:44.599: E/AndroidRuntime(19839): java.lang.IllegalStateException: Can't change tag of fragment SubscribedFragment{41157420 id=0x7f070005 android:switcher:2131165189:0}: was android:switcher:2131165189:0 now android:switcher:2131165189:1
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:398)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:389)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:800)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.view.ViewPager.populate(ViewPager.java:991)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.view.ViewPager.populate(ViewPager.java:880)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1374)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-02 19:15:44.599: E/AndroidRuntime(19839): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2434)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.Choreographer.doFrame(Choreographer.java:532)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.os.Handler.handleCallback(Handler.java:725)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.os.Handler.dispatchMessage(Handler.java:92)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.os.Looper.loop(Looper.java:137)
05-02 19:15:44.599: E/AndroidRuntime(19839): at android.app.ActivityThread.main(ActivityThread.java:5226)
05-02 19:15:44.599: E/AndroidRuntime(19839): at java.lang.reflect.Method.invokeNative(Native Method)
05-02 19:15:44.599: E/AndroidRuntime(19839): at java.lang.reflect.Method.invoke(Method.java:511)
05-02 19:15:44.599: E/AndroidRuntime(19839): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-02 19:15:44.599: E/AndroidRuntime(19839): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-02 19:15:44.599: E/AndroidRuntime(19839): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分:78)
这可能是因为您将相同的片段实例三次添加到列表中。您应该为每个页面创建一个新实例。
此外,如果你不是太过于开发,我建议调查FragmentStatePagerAdapter
。如果要从主活动中刷新片段的内容,则可能是更好的选择。
答案 1 :(得分:7)
以下方法应为每个标签返回一个片段:
@Override
public Fragment getItem(int position) {
//Add some code
//to verify that it will not return null
return listFragment.get(position);
}
代码很好,但请确保listFragment包含三个不同的Fragment,并且该片段不为null。
答案 2 :(得分:2)
可能是您发送的片段实例为null。永远不要将片段实例发送为空。
public static MyFragment getInstance() {
MyFragment myFragment = new MyFragment();
return myFragment;
}
在寻呼机适配器中,始终使用@Override
public Fragment getItem(int position) {
return fragments[position];
}
或
@Override
public Fragment getItem(int position) {
return fragments.get(position);
}
根据您的片段列表。另外,请选择链接FragmentPagerAdapter
注意:- 永远不要将上下文内存用作静态
答案 3 :(得分:0)
您已创建SubscribedFragment()类
的实例savedListFragment = new SubscribedFragment();
然后您将此对象的列表传递给ViewPager Adpater:
FreedomPageAdapter(FragmentManager fm, List<Fragment> listFragment)
在其构造函数中接收Frag of Fragment类型。由于构造函数接收List of Fragment类型,因此在将每个savedListFragment添加到列表中之前,尝试将其转换为Fragment,然后将其传递给adpater的构造函数:
fragmentList.add((Fragment)savedListFragment);
viewPager.setAdapter(new FreedomPageAdapter(fragmentManager(), fragmentList));
答案 4 :(得分:0)
就我而言,我没有为特定位置返回片段实例。 我认为FragmentPagerAdapter收到的空值代替TAG。 这就是为什么它显示“ 无法更改片段标签”的原因 如果我错了请纠正我。
答案 5 :(得分:0)
在我的情况下,这是由于返回了一些空片段,而在getItem(position)函数中未处理该片段。希望对别人有帮助。