java - fragment 中的super.onCreateView

我完成了有关为Android手持系统编程移动应用程序的Coursera类(class)。
本类(class)中的示例代码之一教我们如何分割。基本上，它的工作是将屏幕分为两个部分，一个用于书名，另一个用于书中的引用。如果用户单击左侧 fragment 中的标题，则与书关联的报价将显示在右侧 fragment 中。

这是mainActivity的代码:

package course.examples.Fragments.StaticLayout;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import course.examples.Fragments.StaticLayout.TitlesFragment.ListSelectionListener;

public class QuoteViewerActivity extends Activity implements
        ListSelectionListener {

    public static String[] mTitleArray;
    public static String[] mQuoteArray;
    private QuotesFragment mDetailsFragment;

    private static final String TAG = "QuoteViewerActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mTitleArray = getResources().getStringArray(R.array.Titles);
        mQuoteArray = getResources().getStringArray(R.array.Quotes);

        setContentView(R.layout.main);

        mDetailsFragment = (QuotesFragment) getFragmentManager()
                .findFragmentById(R.id.details);
    }

    @Override
    public void onListSelection(int index) {
        if (mDetailsFragment.getShownIndex() != index) {
            mDetailsFragment.showQuoteAtIndex(index);
        }
    }

这是报价 fragment 的代码:

package course.examples.Fragments.StaticLayout;

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class QuotesFragment extends Fragment {

    private TextView mQuoteView = null;
    private int mCurrIdx = -1;
    private int mQuoteArrayLen;

    private static final String TAG = "QuotesFragment";

    public int getShownIndex() {
        return mCurrIdx;
    }

    public void showQuoteAtIndex(int newIndex) {
        if (newIndex < 0 || newIndex >= mQuoteArrayLen)
            return;
        mCurrIdx = newIndex;
        mQuoteView.setText(QuoteViewerActivity.mQuoteArray[mCurrIdx]);
    }
@Override
public void onAttach(Activity activity) {
    Log.i(TAG, getClass().getSimpleName() + ":entered onAttach()");
    super.onAttach(activity);
}

@Override
public void onCreate(Bundle savedInstanceState) {
    Log.i(TAG, getClass().getSimpleName() + ":entered onCreate()");
    super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    **return inflater.inflate(R.layout.quote_fragment, container, false);**
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mQuoteView = (TextView) getActivity().findViewById(R.id.quoteView);
    mQuoteArrayLen = QuoteViewerActivity.mQuoteArray.length;
}

这是标题 fragment 的代码:

package course.examples.Fragments.StaticLayout;

import android.app.Activity;
import android.app.ListFragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class TitlesFragment extends ListFragment {
    private ListSelectionListener mListener = null;
    private static final String TAG = "TitlesFragment";

    public interface ListSelectionListener {
        public void onListSelection(int index);
    }

    @Override
    public void onListItemClick(ListView l, View v, int pos, long id) {
        getListView().setItemChecked(pos, true);
        mListener.onListSelection(pos);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (ListSelectionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnArticleSelectedListener");
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, getClass().getSimpleName() + ":entered onCreate()");
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        Log.i(TAG, getClass().getSimpleName() + ":entered onCreate()");

        **return super.onCreateView(inflater, container, savedInstanceState);**

    }

    @Override
    public void onActivityCreated(Bundle savedState) {
        super.onActivityCreated(savedState);

        getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        setListAdapter(new ArrayAdapter<String>(getActivity(),
                R.layout.title_item, QuoteViewerActivity.mTitleArray));
    }

MainActivity xml

<?xml version="1.0" encoding="utf-8"?>
<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/titles"
        android:layout_width="0px"
        android:layout_height="match_parent"
        android:layout_weight="1"
        class="course.examples.Fragments.StaticLayout.TitlesFragment" />

    <fragment
        android:id="@+id/details"
        android:layout_width="0px"
        android:layout_height="match_parent"
        android:layout_weight="2"
        class="course.examples.Fragments.StaticLayout.QuotesFragment" />

</LinearLayout>

报价 fragment xml

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

    <TextView
        android:id="@+id/quoteView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="5dip"
        android:textSize="32sp" >
    </TextView>
</LinearLayout>

标题 fragment xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="?android:attr/activatedBackgroundIndicator"
    android:orientation="vertical"
    android:padding="5dip"
    android:textSize="32sp" >

</TextView>

我的问题是为什么onCreateView下的方法在Quote fragment 和Title fragment 下会有所不同？
QuoteFragment是返回inflater.inflate(R.layout.quote_fragment，container，false);
TitleFragment是返回super.onCreateView(inflater，container，savedInstanceState);

最佳答案

因为QuotesFragment扩展了默认情况下不具有布局的Fragment，所以用户必须充气并返回自己的布局。这是onCreateView的Fragment方法的样子:

public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
    return null;
}

TitlesFragment扩展了默认布局的ListFragment，该布局包含项的ListView，列表为空时的标签的TextView和ProgressBar的布局。在这种情况下，用户不必返回自己的 View ，而是可以返回通过 super 调用获得的对象。 onCreateView中的ListFragment:

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    return inflater.inflate(com.android.internal.R.layout.list_content,
            container, false);
}

OnCreateView

java - fragment 中的super.onCreateView