我对Android很陌生。我现在已经坚持这个问题几天了。 我正在使用新的Google操作模板栏标签和滑动（ViewPager）。 在每个片段中，我想显示一张动态卡片列表（带有cardslib：https://github.com/gabrielemariotti/cardslib）。卡的数据来自asyncTask，它从网址获取数据。
这是我的问题：当我启动应用程序时，会显示第一个视图，但ViewPager会为第二个页面准备视图，因此第二个屏幕的异步任务也会启动。第二个屏幕的卡片被添加到第一个屏幕。 然后，如果我滑动到第二个屏幕，则不显示任何内容，并且启动第三个屏幕的异步任务。因此，如果滑动到第三屏幕，没有...然后如果我再次切换到第二个屏幕，显示第一个屏幕的数据的卡片......真是一团糟！
我认为我对onCreate，onCreateView或类似问题有疑问。也许代码有时不在正确的地方..我不知道。我尝试了很多小修改，但没有任何效果。 （但只有动作栏选项卡，没有ViewPager，它就像这样工作。）
由于
这是我的代码：
import java.util.Locale;
import android.app.ActionBar;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v13.app.FragmentPagerAdapter;
import android.support.v13.app.FragmentStatePagerAdapter;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a {@link FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this
* becomes too memory intensive, it may be best to switch to a
* {@link android.support.v13.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mSectionsPagerAdapter.notifyDataSetChanged();
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
//mSectionsPagerAdapter.notifyDataSetChanged();
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
mSectionsPagerAdapter.notifyDataSetChanged();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
if(tab.getPosition() != mViewPager.getCurrentItem()) {
mViewPager.setCurrentItem(tab.getPosition());
}
// mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
mSectionsPagerAdapter.notifyDataSetChanged();
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
mSectionsPagerAdapter.notifyDataSetChanged();
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
}
这是碎片
import it.gmariotti.cardslib.library.internal.Card;
import it.gmariotti.cardslib.library.internal.CardArrayAdapter;
import it.gmariotti.cardslib.library.internal.CardHeader;
import it.gmariotti.cardslib.library.view.CardListView;
import java.util.ArrayList;
import java.util.List;
import android.app.Fragment;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import com.example.webanajones.asyncTask.GetItemTask;
import com.example.webanajones.asyncTask.IResultsListener;
import com.example.webanajones.asyncTaskResponse.ItemJsonResponse;
import com.example.webanajones.asyncTaskResponse.ItemJsonResponse.Item;
/**
* A placeholder fragment containing a simple view.
*/
public class PlaceholderFragment extends Fragment implements
IResultsListener {
/**
* The fragment argument representing the section number for this
* fragment.
*/
static final String ARG_SECTION_NUMBER = "section_number";
public static int limit = 0;
IResultsListener listener = this;
ArrayList<Card> cards = new ArrayList<Card>();
CardArrayAdapter mCardArrayAdapter;
int flag = 0;
boolean loadMore = true;
CardListView listView;
private int idx;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Bundle data = getArguments();
// idx = data.getInt("idx") +1;
limit = 0;
flag = 0;
loadMore = true;
List<String> params = new ArrayList();
params.add(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
params.add(String.valueOf(limit));
GetItemTask getItemTask = new GetItemTask();
getItemTask.setOnResultsListener(listener);
getItemTask.execute(params);
}
/**
* Returns a new instance of this fragment for the given section number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@SuppressWarnings("unchecked")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
@Override
public void onGetItemTaskSucceeded(ItemJsonResponse itemJsonResponse) {
if (mCardArrayAdapter != null) {
mCardArrayAdapter.notifyDataSetChanged();
}
if (itemJsonResponse.getSuccess() != 0) {
loadMore = true;
final Item[] itemTable = itemJsonResponse.getItemArray();
for (int itemIndex = 0; itemIndex < itemTable.length; itemIndex++) {
if (itemTable[itemIndex].getTypeId() == 2) { // 2 = type GIF
final int index = itemIndex;
Card gifCard = new CardGif(getActivity()){
@Override
public void setupInnerViewElements(ViewGroup parent, View view) {
DisplayMetrics metrics = getContext().getResources().getDisplayMetrics();
int width = (int) (metrics.widthPixels * 0.97);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(width, LinearLayout.LayoutParams.WRAP_CONTENT);
params.bottomMargin = 30;
LinearLayout LinearLayout = (LinearLayout) parent.findViewById(R.id.inner_frame);
GIFWebView gifView = new GIFWebView (getActivity(), itemTable[index].getObjectUrl());
LinearLayout.addView(gifView);
}
};
CardHeader header = new CardHeader(getActivity());
header.setTitle(itemTable[itemIndex].getTitle());
cards.add(gifCard);
}
if (itemTable[itemIndex].getTypeId() == 1) { // 1 = image
Card card = new Card(getActivity());
CardHeader header = new CardHeader(getActivity());
header.setTitle(itemTable[itemIndex].getTitle());
card.addCardHeader(header);
MyThumbnail thumb = new MyThumbnail(getActivity(), itemTable[itemIndex].getObjectUrl());
thumb.setExternalUsage(true);
card.addCardThumbnail(thumb);
final int index = itemIndex;
card.addPartialOnClickListener(Card.CLICK_LISTENER_THUMBNAIL_VIEW, new Card.OnCardClickListener() {
@Override
public void onClick(Card card, View view) {
Intent intent = new Intent(getActivity(), FullscreenActivity.class);
intent.putExtra("imageUrl", itemTable[index].getObjectUrl());
startActivity(intent);
}
});
cards.add(card);
}
}
if (flag == 0) {
mCardArrayAdapter = new CardArrayAdapter(getActivity(), cards);
listView = (CardListView) getActivity().findViewById(
R.id.carddemo_list);
listView.setAdapter(mCardArrayAdapter);
flag = 1;
}
}
else {
loadMore = false;
}
loadMoreCards(mCardArrayAdapter, loadMore);
}
public void loadMoreCards(CardArrayAdapter mCardArrayAdapter, boolean loadMore) {
if (listView != null) {
mCardArrayAdapter.notifyDataSetChanged();
if (loadMore) {
listView.setOnScrollListener(new EndlessScrollListener() {
@Override
public void onLoadMore(int page, int totalItemsCount) {
limit += 5;
List<String> params = new ArrayList();
params.add("1");
params.add(String.valueOf(limit));
GetItemTask getItemTask = new GetItemTask();
getItemTask.setOnResultsListener(listener);
getItemTask.execute(params);
}
});
}
}
}
//fin placeholderfrag
@Override
public void onGetImageTaskSucceeded(Bitmap bitmap) {
// TODO Auto-generated method stub
}
}
答案 0 :(得分：0)
谢谢@GabrieleMariotti，它有所帮助！事实上，我已经尝试为不同的片段使用不同的类，但我忘了给我的卡片列表提供不同的ID。它解决了这个问题。顺便说一句，你的lib很好，很棒。
所以对于下一个：为所有不同的片段创建不同的类。他们必须使用不同的布局，而cardsList必须使用不同的ID。