我正在使用ViewPager我的应用程序将一系列列表放在水平滚动条中。但是，当我开始横向滚动并再次返回时，我之前访问过的列表片段是空的。这应该是我编写的加载器重新加载内容的时刻（我对片段和加载器都是新手）。
我已经看到了一些相关的问题，但我不知道如何将它们应用于我的情况。我发现当我用随机 int 替换持有者片段中的 mLayoutID 时，这个示例有效，但是当我这样做时，事情自然会停止工作（比如改变方向）。但它应该对这个问题说些什么。
基本上，listfragment 只是在初始加载后清空并保持为空。
这是我的“持有人”片段：
public final class SceduleFragment extends Fragment {
private static final String KEY_LAYOUT = "SceduleFragment:LayoutID";
private static final String LOG_TAG = "SceduleFragment";
private int mWeekNumber;
private int mLayoutID;
public static SceduleFragment newInstance(String content, int contentID) {
SceduleFragment fragment = new SceduleFragment();
fragment.mWeekNumber = contentID;
fragment.mLayoutID = Integer.parseInt((Integer.toString(Config.WK_PREFIX) + Integer.toString(contentID)));
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_LAYOUT)) {
mLayoutID = savedInstanceState.getInt(KEY_LAYOUT);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
LinearLayout layout = new LinearLayout(getActivity());
layout.setGravity(Gravity.TOP);
layout.setPadding(makeDP(5), makeDP(5), makeDP(5), makeDP(5));
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
layout.setLayoutParams(layoutParams);
LinearLayout innerLayout = new LinearLayout(getActivity());
innerLayout.setBackgroundResource(R.drawable.scd_layout_bg);
LinearLayout.LayoutParams scrollParams = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
innerLayout.setGravity(Gravity.CENTER);
innerLayout.setLayoutParams(scrollParams);
layout.addView(innerLayout);
if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_LAYOUT)) {
mLayoutID = savedInstanceState.getInt(KEY_LAYOUT);
}
Random rand = new Random();
//mLayoutID = rand.nextInt(2000);
innerLayout.setId(mLayoutID);
Log.i(LOG_TAG, "ID for next WeekListFragment " + Integer.toString(mLayoutID));
if (getFragmentManager().findFragmentById(mLayoutID) == null) {
WeekFragment weekFragment = new WeekFragment(mWeekNumber);
getFragmentManager().beginTransaction().add(mLayoutID, weekFragment).commit();
}
return layout;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(KEY_LAYOUT, mLayoutID);
}
private int makeDP(int number){
final float scale = this.getResources().getDisplayMetrics().density;
number = (int) (number * scale + 0.5f);
return number;
}
}
这是在里面创建列表的 ListFragment：
public class WeekFragment extends ListFragment implements
LoaderManager.LoaderCallbacks<Cursor> {
private String LOG_TAG = "WeekFragment";
private static final String KEY_WEEKNR = "SceduleFragment:WeekNumber";
protected Activity mActivity;
protected Cursor mCursor;
protected SceduleDataSource mDataSource;
private int mWeekNumber;
private static final int SCEDULEITEMS_LIST_LOADER = 0x0577;
private static Typeface fontOswaldLight;
private SceduleItemsCursorAdapter mAdapter;
public WeekFragment() { }
public WeekFragment(int weekNumber) {
this.mWeekNumber = weekNumber;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
LoaderManager.enableDebugLogging(true);
mActivity = getActivity();
mDataSource = new SceduleDataSource(mActivity);
fontOswaldLight = Typeface.createFromAsset(mActivity.getAssets(),
"Oswald-Light.otf");
if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_WEEKNR)) {
mWeekNumber = savedInstanceState.getInt(KEY_WEEKNR);
Log.i(LOG_TAG, "Resorting to savestate.");
} else {
Log.i(LOG_TAG, "Saved state was null");
getLoaderManager().initLoader(SCEDULEITEMS_LIST_LOADER, null, this);
mAdapter = new SceduleItemsCursorAdapter(mActivity,
R.layout.scd_lesson_list_item, mCursor, new String[] {
SceduleItems.SCEDULE_DATE,
SceduleItems.SCEDULE_LESSONNAME,
SceduleItems.SCEDULE_BEGIN, SceduleItems.SCEDULE_ROOM,
SceduleItems.SCEDULE_TEACHER,
SceduleItems.SCEDULE_CLASS }, new int[] {
R.id.textDayTitle, R.id.textLessonName,
R.id.textLessonTime, R.id.textLessonRoom,
R.id.textLessonTeacher, R.id.textLessonClass }, 0);
Log.i(LOG_TAG, "Filled WeekListFragment");
setListAdapter(mAdapter);
}
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(KEY_WEEKNR, mWeekNumber);
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ColorDrawable divider = new ColorDrawable(this.getResources().getColor(
R.color.LightGrey));
ListView listView = getListView();
listView.setDivider(divider);
listView.setDividerHeight(makeDP(1));
listView.setLongClickable(true);
listView.setOnItemLongClickListener(new OnItemLongClickListener() {
public boolean onItemLongClick(AdapterView<?> parent, View v,
int position, long id) {
Cursor lessonCursor = (Cursor) getListView().getItemAtPosition(
position);
showLessonDialog(lessonCursor);
return true;
}
});
}
public void showLessonDialog(Cursor lessonCursor) {
String dialogTitle = lessonCursor.getString(2);
final AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(
mActivity);
AlertDialog lessonDialog;
LayoutInflater inflater = (LayoutInflater) mActivity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View dialogLayout = inflater.inflate(R.layout.dlg_lesson_item, null);
TextView textLessonName = (TextView) dialogLayout
.findViewById(R.id.textLessonName);
textLessonName.setText(lessonCursor.getString(2));
TextView textLessonTime = (TextView) dialogLayout
.findViewById(R.id.textLessonTime);
textLessonTime.setText(lessonCursor.getString(6) + " - "
+ lessonCursor.getString(7));
TextView textLessonRoom = (TextView) dialogLayout
.findViewById(R.id.textLessonRoom);
textLessonRoom.setText(lessonCursor.getString(8));
TextView textLessonTeacher = (TextView) dialogLayout
.findViewById(R.id.textLessonTeacher);
textLessonTeacher.setText(lessonCursor.getString(9));
TextView textLessonClass = (TextView) dialogLayout
.findViewById(R.id.textLessonClass);
textLessonClass.setText(lessonCursor.getString(10));
dialogBuilder.setView(dialogLayout).setNeutralButton("Sluit",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
dialog.cancel();
}
});
WebView webView = new WebView(mActivity);
webView = (WebView) dialogLayout.findViewById(R.id.adWebView);
webView.getSettings().setJavaScriptEnabled(true);
webView.setVerticalScrollBarEnabled(false);
webView.setHorizontalScrollBarEnabled(false);
String adHtml = "<html><body>"
+ "<style type='text/css'>body{margin: 0;padding: 0}</style>"
+ "<script type'text/javascript'>"
+ "var admob_vars = {"
+ "pubid: 'xxxxxxxxxx', "
+ "bgcolor: '000000', "
+ "text: 'FFFFFF', "
+ "test: true };"
+ "</script>"
+ "<script type='text/javascript' src='http://mmv.admob.com/static/iphone/iadmob.js'></script></body></html>";
webView.loadData(adHtml, "text/html", "UTF-8");
lessonDialog = dialogBuilder.create();
lessonDialog.setTitle(dialogTitle);
lessonDialog.show();
}
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String dateConverter = "substr(" + SceduleItems.SCEDULE_DATE + ",7)||"
+ "substr(" + SceduleItems.SCEDULE_DATE + ",4,2)||" + "substr("
+ SceduleItems.SCEDULE_DATE + ",1,2)||" + "substr("
+ SceduleItems.SCEDULE_BEGIN + ",1,2)||" + "substr("
+ SceduleItems.SCEDULE_BEGIN + ",4,2)";
CursorLoader cursorLoader = new CursorLoader(getActivity(),
ONTTContentProvider.CONTENT_URI, mDataSource.allSceduleColumns,
SceduleItems.SCEDULE_WEEKCODE + " like '" + mWeekNumber + "'",
null, dateConverter + " ASC");
return cursorLoader;
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
mAdapter.swapCursor(cursor);
Log.i(LOG_TAG, "Finished with loading week " + Integer.toString(mWeekNumber));
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
mAdapter.swapCursor(null);
}
private int makeDP(int number) {
final float scale = this.getResources().getDisplayMetrics().density;
number = (int) (number * scale + 0.5f);
return number;
}
public class SceduleItemsCursorAdapter extends SimpleCursorAdapter {
private LayoutInflater layoutInflater;
private int layout;
public SceduleItemsCursorAdapter(Context context, int layout, Cursor cursor,
String[] from, int[] to, int flags) {
super(context, layout, cursor, from, to, flags);
this.layout = layout;
layoutInflater = LayoutInflater.from(context);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
View view = layoutInflater.inflate(layout, parent, false);
return view;
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
String viewID = Config.SI_PREFIX + cursor.getString(0);
view.setId(Integer.parseInt(viewID));
LinearLayout dayHeader = (LinearLayout) view.findViewById(R.id.layoutDayTitle);
TextView dayTitle = (TextView) view.findViewById(R.id.textDayTitle);
TextView lessonName = (TextView) view.findViewById(R.id.textLessonName);
TextView lessonTime = (TextView) view.findViewById(R.id.textLessonTime);
TextView lessonRoom = (TextView) view.findViewById(R.id.textLessonRoom);
TextView lessonTeacher = (TextView) view.findViewById(R.id.textLessonTeacher);
TextView lessonClass = (TextView) view.findViewById(R.id.textLessonClass);
lessonName.setText(cursor.getString(2));
lessonTime.setText(cursor.getString(6) + " - " + cursor.getString(7));
lessonRoom.setText(cursor.getString(8));
lessonTeacher.setText(cursor.getString(9));
lessonClass.setText(cursor.getString(10));
String thisDate = cursor.getString(5);
String prevDate = null;
if (cursor.getPosition() > 0 && cursor.moveToPrevious()) {
prevDate = cursor.getString(5);
cursor.moveToNext();
}
if (prevDate == null || !prevDate.equals(thisDate)) {
dayHeader.setVisibility(View.VISIBLE);
String dayName = Config.Days[Integer.parseInt(cursor.getString(3))];
dayName += " " + cursor.getString(5);
dayTitle.setText(dayName);
dayTitle.setTypeface(fontOswaldLight);
} else {
dayHeader.setVisibility(View.GONE);
}
if((Config.SI_PREFIX + ONTTShowScedule.upcomingItemID).equals(viewID)) {
int redColor = getResources().getColor(R.color.DarkRed);
lessonName.setTextColor(redColor);
lessonTime.setTextColor(redColor);
lessonRoom.setTextColor(redColor);
lessonTeacher.setTextColor(redColor);
lessonClass.setTextColor(redColor);
}
}
}
}