android - 无法用另一个 fragment 替换一个 fragment

Question

即使我一直在阅读有关我的问题的其他主题，我也无法找出我的问题的原因。

我有一个 Activity ，左边有一个 ListView。右侧是一个 ListFragment，您可以在 activity_question.xml 中看到它:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="3"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/textViewCategoryTitle"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:layout_weight="10"
                android:background="@drawable/in_progress_background"
                android:gravity="center" />

            <ListView
                android:id="@+id/listViewQuestionsGroup"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1" />
        </LinearLayout>

        <fragment
            android:id="@+id/fragmentQuestions"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            class="com.firm.bonjour.visite.QuestionsFragment" />
    </LinearLayout>

    <Button
        android:id="@+id/buttonValidate"
        style="@style/ButtonsValidation"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:text="@string/validate" />

</LinearLayout>

我已经为 fragment 的 ListView 创建了一个适配器:

public class QuestionsAdapter extends BaseAdapter {

    private QuestionsBean questions = null;
    private LayoutInflater inflater = null;

    public QuestionsAdapter(LayoutInflater inflater) {
        this.inflater = inflater;
    }

    @Override
    public int getCount() {
        return (questions != null && questions.getQuestionList() != null) ? questions.getQuestionList().size() : 0;
    }

    @Override
    public Object getItem(int position) {
        return (questions != null && questions.getQuestionList() != null) ? questions.getQuestionList().get(position) : null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        if (convertView == null) {
            holder = new ViewHolder();

            convertView = inflater.inflate(R.layout.item_fragment_question, null);

            holder.question = (TextView) convertView.findViewById(R.id.questionsLayout);

            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.question.setText(((QuestionsBean) questions).getQuestionList().get(position).getQuestion());

        return convertView;
    }

    private class ViewHolder {
        TextView question;
    }

    public void setQuestions(QuestionsBean questions) {
        this.questions = questions;
        notifyDataSetChanged();
    }

}

当我启动 Activity 时，我选择左侧 ListView 的第一项以在 Fragment 中显示详细信息。单击左侧 ListView 的其中一项后， fragment 不会更改。当我在 Debug模式时，我可以看到适配器获得了正确的对象来显示。

您知道为什么新 fragment 没有显示吗？

我的 Activity 代码:

public class QuestionsActivity extends Activity implements OnItemClickListener {

    public static final String QUESTIONS_LIST = "questionsList";
    public static final String QUESTIONS = "questions";

    private CategoryBean category;

    private ListView questionsGroupListView;

    private Fragment questionsFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_questions);

        category = (CategoryBean) getIntent().getExtras().get(MainActivity.CATEGORY);

        questionsGroupListView = (ListView) findViewById(R.id.listViewQuestionsGroup);
        QuestionListAdapter adapter = new QuestionListAdapter(this, category);
        questionsGroupListView.setAdapter(adapter);
        questionsGroupListView.setOnItemClickListener(this);

        if (getFragmentManager().findFragmentById(R.id.fragmentQuestions) == null) {
            questionsFragment = new QuestionsFragment();
            getFragmentManager().beginTransaction().add(R.layout.activity_questions, questionsFragment).commit();
        } else {
            questionsFragment = getFragmentManager().findFragmentById(R.id.fragmentQuestions);
        }
    }

    /**
     * Called when a number gets clicked
     */
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        displayFragment((QuestionsBean)questionsGroupListView.getItemAtPosition(position));
    }

    @Override
    protected void onResume() {
        super.onResume();
        if(questionsFragment != null && category.getCategoryList() != null && !category.getCategoryList().isEmpty()) {
            ((QuestionsFragment)questionsFragment).refresh((QuestionsBean)category.getCategoryList().get(0));
        } else {
            Log.v("BUGGGGG", "PAS NORMAL !!!");
        }
    }

    /**
     * Add a Fragment to our stack with n Androids in it
     */
    private void displayFragment(QuestionsBean questions) {
        Fragment fragment = QuestionsFragment.newInstance(questions);

        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.fragmentQuestions, fragment);
        fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        fragmentTransaction.commit();
    }

}

我的 ListFragment 代码:

public class QuestionsFragment extends ListFragment {

    private LayoutInflater inflater;
    private QuestionsAdapter adapter;
    private QuestionsBean questions;

    /**
     * Create a new instance of DetailsFragment, initialized to show the text at 'index'.
     */
    public static QuestionsFragment newInstance(QuestionsBean questions) {
        QuestionsFragment questionFragment = new QuestionsFragment();

        // Supply index input as an argument.
        Bundle args = new Bundle();
        args.putSerializable(QuestionsActivity.QUESTIONS, questions);
        questionFragment.setArguments(args);

        return questionFragment;
    }

    public int getShownIndex() {
        return getArguments() != null ? getArguments().getInt("index", 0) : 0;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        this.inflater = inflater;
        this.adapter = new QuestionsAdapter(inflater);

        View questionsView = (LinearLayout) inflater.inflate(R.layout.layout_fragment_question, null);
        setListAdapter(adapter);

        return questionsView;
    }

    @Override
    public void onResume() {
        super.onResume();
        if (getArguments() != null && getArguments().getSerializable(QuestionsActivity.QUESTIONS) != null) {
            this.questions = (QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS);
            adapter.setQuestions((QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS));
        } else {
            adapter.setQuestions(questions);
        }
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

    }

    public void refresh(QuestionsBean questions) {
        if (getArguments() != null && getArguments().getSerializable(QuestionsActivity.QUESTIONS) != null) {
            this.questions = (QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS);
        } else {
            this.questions = questions;
        }
    }

}

我现在真的被困了好几个小时......非常感谢任何帮助:)

Answer 1

首先，由于您正在使用 fragment 的 Argument 包来存储数据，因此请确保它可以正确序列化 - 检查嵌入的 questions.getQuestionList() 是否不为 null 或其他内容。

如果每次单击 listItem 时都需要一个新的 fragment ，那么您最好将参数 bean 直接存储为 fragment 的一个属性，至少作为一种临时措施，直到您发现问题所在。

public static QuestionsFragment newInstance(QuestionsBean questions) {
    QuestionsFragment questionFragment = new QuestionsFragment();
    questionFragment.questions = questions;
    return questionFragment;
}

其次，尝试协调 fragment 的 onResume() 中的刷新代码和 fragment 的 refresh() 中的刷新代码，也许让 onResume 调用 refresh()。还要确保您的 refresh() 代码更新了您的适配器，以便您可以实际显示任何新值。如果您放弃使用 Argument Bundle(至少在您找到错误之前)，代码会变得简单得多。

@Override
public void onResume() {
    super.onResume();
    refresh(this.questions);
}

public void refresh(QuestionsBean questions) {
    this.questions = questions;
    adapter.setQuestions(questions);
}

最后一步是您的 Activity 代码 - 尝试删除所有在 displayFragment 方法之外提及 QuestionsFragment 的代码。只需从 Activity 的 onResume() 和 listItemClick 事件中调用 displayFragment。

使用这种代码，新的 QuestionFragment 将由 Activity 的 onCreate 的 LayoutInflater 分配一次，然后在 onResume 期间替换为默认类别问题，然后在每次单击后替换为所选类别。然后，您可以更轻松地跟踪真正发生的事情，并可能从那里开始构建？

从那时起，我将亲自调整 displayFragment 方法以检查 QuestionFragment 是否存在，然后刷新它而不是用新的替换它。

祝你好运，告诉我们进展如何!