我有一个带有两个片段的活动，左边的一个是静态的，并在GridView中显示类别的名称;我在右侧有一个framelayout，可以根据需要保存动态片段。最初它显示一个片段TopicListFragment（一个带有类别主题的listView），然后单击CREATE类别按钮（这在左侧的GridView上方）右侧的TopicListFragment被另一个片段FormCreateCategoryFragment替换。现在，如果我单击左侧gridView中的任何类别，则此FormCreateCategoryFragment应再次被TopicListFragment替换，以显示所单击类别的主题，但应用程序崩溃时出现以下错误---
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01-02 11:11:33.564: W/dalvikvm(2466): threadid=1: thread exiting with uncaught exception (group=0x409f41f8)
01-02 11:11:33.574: E/AndroidRuntime(2466): FATAL EXCEPTION: main
01-02 11:11:33.574: E/AndroidRuntime(2466): java.lang.ClassCastException: com.gitanjal.together.view.FormCreateCategoryFragment cannot be cast to com.gitanjal.together.view.TopicListFragment
01-02 11:11:33.574: E/AndroidRuntime(2466): at com.gitanjal.together.view.CategoryListFragment.showTopics(CategoryListFragment.java:145)
01-02 11:11:33.574: E/AndroidRuntime(2466): at com.gitanjal.together.view.CategoryListFragment.access$1(CategoryListFragment.java:139)
01-02 11:11:33.574: E/AndroidRuntime(2466): at com.gitanjal.together.view.CategoryListFragment$2.onItemClick(CategoryListFragment.java:93)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.widget.AdapterView.performItemClick(AdapterView.java:292)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.widget.AbsListView.performItemClick(AbsListView.java:1058)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2514)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.widget.AbsListView$1.run(AbsListView.java:3168)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.os.Handler.handleCallback(Handler.java:605)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.os.Handler.dispatchMessage(Handler.java:92)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.os.Looper.loop(Looper.java:137)
01-02 11:11:33.574: E/AndroidRuntime(2466): at android.app.ActivityThread.main(ActivityThread.java:4424)
01-02 11:11:33.574: E/AndroidRuntime(2466): at java.lang.reflect.Method.invokeNative(Native Method)
01-02 11:11:33.574: E/AndroidRuntime(2466): at java.lang.reflect.Method.invoke(Method.java:511)
01-02 11:11:33.574: E/AndroidRuntime(2466): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-02 11:11:33.574: E/AndroidRuntime(2466): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-02 11:11:33.574: E/AndroidRuntime(2466): at dalvik.system.NativeStart.main(Native Method)
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import org.json.JSONException;
import org.json.JSONObject;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.GridView;
import android.widget.Toast;
import com.gitanjal.together.request.RequestHandler;
/*
* CLASS:CategoryListFragment
* PURPOSE:This is a fragment to display the list of categories
* */
public class CategoryListFragment extends Fragment {
RequestHandler newRequest = new RequestHandler(); // Create an object to
// make the requests to
// RequestHandler
Context contextParent = this.getActivity(); ///context of the parent activity
int noOfCategories=0;
//String responseArray[];
Button btnCreateCategory;
boolean mDualPane;
int mCurCheckPosition = 0;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
System.out.println("Category list activity extends fragment");
newRequest.requestGetCategories(contextParent,this); //Make the request
return inflater.inflate(R.layout.category_grids, null, false);
}
@Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
//Get the create category button
Button btnCreateCategory=(Button) getActivity().findViewById(R.id.btnCreateCategory);
btnCreateCategory.setOnClickListener(new OnClickListener() {
//On clicking the Create category button display the fragment containing the Category create form : FormCreateCategoryFragment
public void onClick(View v) {
showCreateCategoryForm();
}
});
}
public void handleResponse(JSONObject response)
{
try {
System.out.println("Back inside the caller THE CATEGORYLISTFRAGMENT: no of contents in the json--"+response.length());
noOfCategories=response.length();
String responseArray[]=new String[noOfCategories];
for(int i=0;i<noOfCategories;i++)
{
responseArray[i]=response.getString("item"+i+"");
System.out.println(i+":"+responseArray[i]+"\n");
}
/*
*Display the category names in the grid
* */
GridView categoryList=(GridView)getActivity().findViewById(R.id.gridview);
ArrayAdapter<String> adapter=new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_1,responseArray);
categoryList.setAdapter(adapter);
categoryList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1,int position, long arg3) {
showTopics(position);
}
});
/*
* Check if in dual pane mode
* */
View listTopics=getActivity().findViewById(R.id.topics);
mDualPane=(listTopics!=null && listTopics.getVisibility()==View.VISIBLE);
Toast.makeText(getActivity(), "mdualpane:"+mDualPane, Toast.LENGTH_LONG).show();
if (mDualPane) {
// In dual-pane mode, the list view highlights the selected
// item.
Fragment fr=(Fragment)getFragmentManager().findFragmentById(R.id.topics);
if(fr instanceof FormCreateCategoryFragment)
{
System.out.println("Create Category Form was displayed");
showCreateCategoryForm();
}
else if(fr instanceof TopicListFragment)
{
showTopics(mCurCheckPosition);
}
} else {
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void showTopics(int index) {
// TODO Auto-generated method stub
mCurCheckPosition = index;
if(mDualPane)
{
TopicListFragment topicListFragment=(TopicListFragment)getFragmentManager().findFragmentById(R.id.topics);
if(topicListFragment==null || topicListFragment.getShownIndex()!=index)
{
FragmentManager fm=getFragmentManager();
topicListFragment=TopicListFragment.newInstance(index);
android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.topics, topicListFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
}
else
{
}
}
else
{
System.out.println("The index is:"+index+"\nThe mCurCheckPos:"+mCurCheckPosition+"\n");
Intent intent=new Intent(getActivity(),TopicsByCategoryActivity.class);
intent.putExtra("index", mCurCheckPosition);
startActivity(intent);
}
}
private void showCreateCategoryForm() {
// TODO Auto-generated method stub
if(mDualPane)
{
FormCreateCategoryFragment formCreateCategory=new FormCreateCategoryFragment();
android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.topics, formCreateCategory);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
}
else
{
System.out.println("In single pane mode : going to display create category form");
Intent intent=new Intent(getActivity(),FormCreateCategoryActivity.class);
intent.putExtra("index", mCurCheckPosition);
startActivity(intent);
}
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
}
}
============================================
我正在尝试不同的方法来解决这个问题，但却无法解决这个问题。使用片段管理器有什么问题吗？
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FormCreateCategoryFragment：
public class FormCreateCategoryFragment extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
return inflater.inflate(R.layout.fragment_form_create_category, container, false);
}
@Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
System.out.println("\nInside onStart of the FormCreateCategoryFragment===============\n");
}
}
=============================================== ================
activity_home xml：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:orientation="horizontal" >
<fragment
android:id="@+id/cat_list_home"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
class="com.gitanjal.together.view.CategoryListFragment" />
<FrameLayout
android:id="@+id/topics"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
/>
</LinearLayout>
答案 0 :(得分：0)
将xml中的片段声明为
<FrameLayout
android:id="@+id/topics_fragment"
android:layout_width="wrap_parent"
android:layout_height="wrap_parent"
>
</FrameLayout>
并执行像这样的片段交易
FragmentTransaction ft = getSupportFragmentManager()
.beginTransaction();
ft.replace(R.id.topics_fragment, new FormCreateCategoryFragment());
ft.commit();
通过使用TopicsFragment重新编写
来执行片段事务单击categoryList项时，您不检查实例的类型
categoryList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1,int position, long arg3) {
here is the problem
do the same here
Fragment fr=(Fragment)getFragmentManager().findFragmentById(R.id.topics);
if(fr instanceof FormCreateCategoryFragment)
{
System.out.println("Create Category Form was displayed");
showCreateCategoryForm();
}
else if(fr instanceof TopicListFragment)
{
showTopics(position);
}
}
});
答案 1 :(得分：0)
请使用replace（id，fragmentInstance，tagStr）api，你可以使用findFragmentByTag（tag）方法按标签查找片段
答案 2 :(得分：0)
我已经解决了我的问题----
private void showTopics(int index) {
// TODO Auto-generated method stub
mCurCheckPosition = index;
if(mDualPane)
{
//---------------------------------------------
Fragment fr= (Fragment)getFragmentManager().findFragmentById(R.id.topics);
if(fr instanceof TopicListFragment)
{
TopicListFragment topicListFragment=(TopicListFragment)getFragmentManager().findFragmentById(R.id.topics);
if(topicListFragment==null || topicListFragment.getShownIndex()!=index)
{
FragmentManager fm=getFragmentManager();
topicListFragment=TopicListFragment.newInstance(index);
android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.topics, topicListFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
}
else
{
}
}
else
{
android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.topics, TopicListFragment.newInstance(index));
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
}
}