CustomLoaderでWebページをスクレイプするアクティビティがあります。ローダーが終了したら、取得したデータで3つのタブの内容を更新したいと思います。
android devサンプルによって提供されるサンプルコードを使用して、アクティビティにViewpager / Tabs/Fragmentsを実装しています。
タブのフラグメントが作成されると、onCreateViewが正しく呼び出され、ビュー上のすべてのウィジェットが正しく配置され、変数にマップされます。
ただし、アクティビティからフラグメントを検索し、フラグメントのメソッドを呼び出してその内容を更新しようとすると、変数はnullになります。さらに、getViewを呼び出すとnullも返されます-TabsAdapterから取得しているフラグメントのインスタンスは、インスタンス化された正しいインスタンスではありませんか？
コードを単一のタブフラグメントに切り詰めました。問題のコードは、フラグメントを更新するためのonLoaderFinishedからの呼び出しです。
3つのタブフラグメントすべてに単一のローダーからのデータが入力されるため、ローダーはフラグメントではなくアクティビティにあります。新しいデータをペイントするようにフラグメントに指示する方法が必要です。
public class InfoBloodStocksActivity extends SherlockFragmentActivity
implements LoaderManager.LoaderCallbacks<BloodStocksLoaderResponse> {
TabHost mTabHost;
ViewPager mViewPager;
TabsAdapter mTabsAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.info_bloodstocks_tabpager);
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mViewPager = (ViewPager)findViewById(R.id.infoBloodStocksTabPager);
mViewPager.setOffscreenPageLimit(3);
mTabsAdapter = new TabsAdapter(this, mTabHost, mViewPager);
mTabsAdapter.addTab(mTabHost.newTabSpec("Daily stock").setIndicator("Daily stocks"),
InfoBloodStocksPageFragment.class, null);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
}
loadStockDetailsFromWebsite();
}
private void loadStockDetailsFromWebsite() {
// Prepare the loader. Either re-connect with an existing one,
// or start a new one.
getSupportLoaderManager().initLoader(0, null, this);
}
@Override
public Loader<BloodStocksLoaderResponse> onCreateLoader(int arg0, Bundle arg1) {
// This is called when a new Loader needs to be created. This
// sample only has one Loader with no arguments, so it is simple.
return new BloodStocksCustomLoader(this);
}
@Override
public void onLoadFinished(Loader<BloodStocksLoaderResponse> loader, BloodStocksLoaderResponse response) {
if (response.isNewStocksLoaded()) {
InfoBloodStocksPageFragment fragment = (InfoBloodStocksPageFragment) mTabsAdapter.getItem(0);
fragment.setNewImage(response.getDailyStocksImageURL());
}
}
@Override
public void onLoaderReset(Loader<BloodStocksLoaderResponse> arg0) {
// TODO Auto-generated method stub
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("tab", mTabHost.getCurrentTabTag());
}
/**
* This is a helper class that implements the management of tabs and all
* details of connecting a ViewPager with associated TabHost. It relies on a
* trick. Normally a tab host has a simple API for supplying a View or
* Intent that each tab will show. This is not sufficient for switching
* between pages. So instead we make the content part of the tab host
* 0dp high (it is not shown) and the TabsAdapter supplies its own dummy
* view to show as the tab content. It listens to changes in tabs, and takes
* care of switch to the correct paged in the ViewPager whenever the selected
* tab changes.
*/
public static class TabsAdapter extends FragmentPagerAdapter
implements TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener {
private final Context mContext;
private final TabHost mTabHost;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
static final class TabInfo {
private final String tag;
private final Class<?> clss;
private final Bundle args;
TabInfo(String _tag, Class<?> _class, Bundle _args) {
tag = _tag;
clss = _class;
args = _args;
}
}
static class DummyTabFactory implements TabHost.TabContentFactory {
private final Context mContext;
public DummyTabFactory(Context context) {
mContext = context;
}
@Override
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
public TabsAdapter(FragmentActivity activity, TabHost tabHost, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mTabHost = tabHost;
mViewPager = pager;
mTabHost.setOnTabChangedListener(this);
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
tabSpec.setContent(new DummyTabFactory(mContext));
String tag = tabSpec.getTag();
TabInfo info = new TabInfo(tag, clss, args);
mTabs.add(info);
mTabHost.addTab(tabSpec);
notifyDataSetChanged();
}
@Override
public int getCount() {
return mTabs.size();
}
@Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
}
@Override
public void onTabChanged(String tabId) {
int position = mTabHost.getCurrentTab();
mViewPager.setCurrentItem(position);
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
// Unfortunately when TabHost changes the current tab, it kindly
// also takes care of putting focus on it when not in touch mode.
// The jerk.
// This hack tries to prevent this from pulling focus out of our
// ViewPager.
TabWidget widget = mTabHost.getTabWidget();
int oldFocusability = widget.getDescendantFocusability();
widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);
mTabHost.setCurrentTab(position);
widget.setDescendantFocusability(oldFocusability);
}
@Override
public void onPageScrollStateChanged(int state) {
}
}
}
アクティビティからsetNewImageを呼び出しています。
public class InfoBloodStocksPageFragment extends SherlockFragment {
private ImageView mImageView;
private ProgressBar mProgress;
private TextView mTitle;
private TextView mDescriptionText;
private String mImageURL;
private ImageLoader mImageLoader = ImageLoader.getInstance();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.info_bloodstocks_page, container, false);
mImageView = (ImageView)view.findViewById(R.id.bloodStocksPageImage);
mProgress = (ProgressBar)view.findViewById(R.id.bloodStocksPageProgress);
mTitle = (TextView)view.findViewById(R.id.bloodStockPageTitle);
mDescriptionText = (TextView)view.findViewById(R.id.bloodStocksPageText);
mProgress.setVisibility(View.VISIBLE);
mDescriptionText.setVisibility(View.GONE);
return view;
}
public void setNewImage(String imageURL) {
// why is mImageView null here ?
// why does getView() return null here ?
View view = getView();
mImageView = (ImageView)view.findViewById(R.id.bloodStocksPageImage);
DisplayImageOptions displayImageOptions = new DisplayImageOptions.Builder()
.showImageForEmptyUri(R.drawable.loading_stock_figures)
.cacheOnDisc()
.imageScaleType(ImageScaleType.EXACT)
.build();
mImageLoader.displayImage(imageURL, mImageView, displayImageOptions, new ImageLoadingListener() {
@Override
public void onLoadingStarted() {
mProgress.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingFailed(FailReason failReason) {
String message = null;
switch (failReason) {
case IO_ERROR:
message = "Input/Output error";
break;
case OUT_OF_MEMORY:
message = "Out Of Memory error";
break;
case UNKNOWN:
message = "Unknown error";
break;
}
mProgress.setVisibility(View.GONE);
mImageView.setImageResource(android.R.drawable.ic_delete);
}
@Override
public void onLoadingComplete() {
mProgress.setVisibility(View.GONE);
Animation anim = AnimationUtils.loadAnimation(getActivity(), R.anim.fade_in);
mImageView.setAnimation(anim);
anim.start();
}
@Override
public void onLoadingCancelled() {
// Do nothing
}
});
}
}