I have a `cursorLoader` which is working fine.
问题是我没有像我想的那样使用它,我将数据从cursorLoader加载到arrayLists然后使用列表.
我发现这个教程展示了如何将cursorLoader与viewPager一起使用,但我不明白如何实现它.
http://tumble.mlcastle.net/post/25875136857/bridging-cursorloaders-and-viewpagers-on-android
我有一个片段,看起来像这样：
public class FirstFragment extends Fragment {
MapView mapView;
GoogleMap map;
// Store instance variables
private String email,about,imagepath,latitude,longitude;
Button getDirections;
// newInstance constructor for creating fragment with arguments
public static FirstFragment newInstance(String email,String about,String imagepath,String latitude,String longitude) {
FirstFragment fragmentFirst = new FirstFragment();
Bundle args = new Bundle();
args.putString("email",email);
args.putString("about",about);
args.putString("imagepath",imagepath);
args.putString("latitude",latitude);
args.putString("longitude",longitude);
fragmentFirst.setArguments(args);
return fragmentFirst;
}
// Store instance variables based on arguments passed
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
email = getArguments().getString("email");
about = getArguments().getString("about");
imagepath = getArguments().getString("imagepath");
latitude = getArguments().getString("latitude");
longitude = getArguments().getString("longitude");
}
// Inflate the view for the fragment based on layout XML
@Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,final Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.zzfragment_pager_items,container,false);
ImageView imageView = (ImageView) view.findViewById(R.id.listpager_imageView);
TextView about = (TextView) view.findViewById(R.id.listpager_text);
TextView emaill = (TextView) view.findViewById(R.id.listpager_title);
about.setText(this.about);
emaill.setText(this.email);
ImageLoader imageLoader = ImageLoader.getInstance();
displayImageOptions options = new displayImageOptions.Builder().cacheInMemory(true)
.cacheOndisc(true).resetViewBeforeLoading(true)
.considerExifParams(true)
.build();
imageLoader.getInstance().displayImage(imagepath,imageView,options);
getDirections = (Button) view.findViewById(R.id.getdirections);
getDirections.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String strUri = "http://maps.google.com/maps?q=loc:" + latitude + "," + longitude + " (" + email + ")";
Intent mapIntent = new Intent(android.content.Intent.ACTION_VIEW,Uri.parse(strUri));
mapIntent.setClassName("com.google.android.apps.maps","com.google.android.maps.MapsActivity");
getActivity().startActivity(mapIntent);
}
});
// View v = inflater.inflate(R.layout.listviewtopager,false);
// Gets the MapView from the XML layout and creates it
mapView = (MapView) view.findViewById(R.id.mapview);
mapView.onCreate(savedInstanceState);
// Gets to GoogleMap from the MapView and does initialization stuff
map = mapView.getMap();
map.getUiSettings().setMyLocationButtonEnabled(false);
map.setMyLocationEnabled(true);
// Needs to call MapsInitializer before doing any CameraUpdateFactory calls
MapsInitializer.initialize(this.getActivity());
// Updates the location and zoom of the MapView
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(new LatLng(Double.parseDouble(latitude),Double.parseDouble(longitude)),10);
map.animateCamera(cameraUpdate);
return view;
}
@Override
public void onResume() {
mapView.onResume();
super.onResume();
}
@Override
public void onDestroy() {
super.onDestroy();
mapView.onDestroy();
}
@Override
public void onLowMemory() {
super.onLowMemory();
mapView.onLowMemory();
}
}
而我在这堂课中称它为：
public class ViewPagerFragment extends FragmentActivity implements
LoaderManager.LoaderCallbacks<Cursor>{
ArrayList<String> e
mail = new ArrayList<String>();
ArrayList<String> about = new ArrayList<String>();
ArrayList<String> imagepath = new ArrayList<String>();
ArrayList<String> latitude = new ArrayList<String>();
ArrayList<String> longitude = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_pager_fragment);
getLoaderManager().initLoader(1,null,this);
}
private SmartFragmentStatePagerAdapter adapterViewPager;
// Extend from SmartFragmentStatePagerAdapter Now instead for more dynamic ViewPager items
public static class MyPagerAdapter extends SmartFragmentStatePagerAdapter {
private final ArrayList<String> email;
private final ArrayList<String> about;
private final ArrayList<String> imagepath;
private final ArrayList<String> latitude;
private final ArrayList<String> longitude;
private int listPosition;
public MyPagerAdapter(FragmentManager fragmentManager,ArrayList<String> email,ArrayList<String> about,ArrayList<String> imagepath,ArrayList<String> latitude,ArrayList<String> longitude,int lPosition) {
super(fragmentManager);
this.imagepath=imagepath;
this.email=email;
this.about = about;
this.latitude= latitude;
this.longitude = longitude;
listPosition = lPosition;
}
// Returns total number of pages
@Override
public int getCount() {
return email.size();
}
// Returns the fragment to display for that page
@Override
public Fragment getItem(int position) {
// return FirstFragment.newInstance(listPosition+position,email.get(listPosition+position));
return FirstFragment.newInstance(email.get(position),about.get(position),imagepath.get(position),latitude.get(position),longitude.get(position));
}
// Returns the page title for the top indicator
@Override
public CharSequence getPageTitle(int position) {
return "Page " + position;
}
}
@Override
public Loader<Cursor> onCreateLoader(int id,Bundle args) {
String[] projection =
{
ActivitiesTable.KEY_EMAIL,ActivitiesTable.KEY_ABOUT,ActivitiesTable.KEY_IMAGEPATH,ActivitiesTable.KEY_LATITUDE,ActivitiesTable.KEY_LONGITUTDE
};
CursorLoader cursorLoader = new CursorLoader(this,NameContentProvider.NAME_ACTIVITIES_URI,projection,null);
return cursorLoader;
}
@Override
public void onLoadFinished(android.content.Loader<Cursor> loader,Cursor cursor) {
if (cursor != null && cursor.getCount() > 0) {
cursor.movetoFirst();
do {
email.add(cursor.getString(cursor
.getColumnIndexOrThrow("email")));
about.add(cursor.getString(cursor
.getColumnIndexOrThrow("about")));
imagepath.add(cursor.getString(cursor
.getColumnIndexOrThrow("imagepath")));
latitude.add(cursor.getString(cursor
.getColumnIndexOrThrow("serverLatitude")));
longitude.add(cursor.getString(cursor
.getColumnIndexOrThrow("serverLongitude")));
} while (cursor.movetoNext());
}
int listPosition = getIntent().getExtras().getInt("position");
ViewPager vpPager = (ViewPager) findViewById(R.id.vpPager);
adapterViewPager = new MyPagerAdapter(getSupportFragmentManager(),email,longitude,listPosition);
vpPager.setAdapter(adapterViewPager);
vpPager.setCurrentItem(listPosition);
}
@Override
public void onLoaderReset(android.content.Loader<Cursor> loader) {
}
}
如何修改代码以使用该教程直接将viewPager与加载器一起使用,而不是将所有内容存储在列表中然后使用列表？
解决方法
我无法评论,所以我正在写一个答案..
您有一个实现LoaderCallbacks< Cursor>的活动.加载数据时,您的活动会收到onLoadFinished回调.在此方法中,您有一个应该在ViewPager中显示的Cursor.
要显示Cursor中的数据,请在适配器上调用swapCursor方法.因此,每次加载数据时都不要创建适配器.创建一次,然后只需调用swapCursor即可.
此外,每次都找不到ViewPager – findViewById是一个繁重的操作,它应该在创建视图层次结构后执行.
所以,你的onLoadFinished将如下所示：
@Override
public void onLoadFinished(android.content.Loader<Cursor> loader,Cursor cursor) {
if (adapterViewPager == null) {
adapterViewPager = new MyPagerAdapter(getSupportFragmentManager(),cursor);
vpPager.setAdapter(adapterViewPager);
} else {
adapterViewPager.swapCursor(cursor);
}
}