Android 作为ViewPager的一部分更新ListFragment中的数据
我正在Android中使用v4兼容ViewPager。我的FragmentActivity有一组数据,这些数据将以不同的方式显示在我的ViewPager的不同页面上。到目前为止,我只有3个相同ListFragment的实例,但将来我将有3个不同ListFragment的实例。ViewPager位于垂直电话屏幕上,列表不是并排的 现在,ListFragment上的一个按钮启动一个单独的完整页面活动(通过FragmentActivity),该活动返回数据,FragmentActivity修改数据,保存数据,然后尝试更新其ViewPager中的所有视图。就在这里,我被困在这里Android 作为ViewPager的一部分更新ListFragment中的数据,android,android-fragments,android-viewpager,android-adapter,android-listfragment,Android,Android Fragments,Android Viewpager,Android Adapter,Android Listfragment,我正在Android中使用v4兼容ViewPager。我的FragmentActivity有一组数据,这些数据将以不同的方式显示在我的ViewPager的不同页面上。到目前为止,我只有3个相同ListFragment的实例,但将来我将有3个不同ListFragment的实例。ViewPager位于垂直电话屏幕上,列表不是并排的 现在,ListFragment上的一个按钮启动一个单独的完整页面活动(通过FragmentActivity),该活动返回数据,FragmentActivity修改数据,保
public class ProgressMainActivity extends FragmentActivity
{
MyAdapter mAdapter;
ViewPager mPager;
@Override
public void onCreate(Bundle savedInstanceState)
{
...
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.viewpager);
mPager.setAdapter(mAdapter);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
...
updateFragments();
...
}
public void updateFragments()
{
//Attempt 1:
//mAdapter.notifyDataSetChanged();
//mPager.setAdapter(mAdapter);
//Attempt 2:
//HomeListFragment fragment = (HomeListFragment) getSupportFragmentManager().findFragmentById(mAdapter.fragId[0]);
//fragment.updateDisplay();
}
public static class MyAdapter extends FragmentPagerAdapter implements
TitleProvider
{
int[] fragId = {0,0,0,0,0};
public MyAdapter(FragmentManager fm)
{
super(fm);
}
@Override
public String getTitle(int position){
return titles[position];
}
@Override
public int getCount(){
return titles.length;
}
@Override
public Fragment getItem(int position)
{
Fragment frag = HomeListFragment.newInstance(position);
//Attempt 2:
//fragId[position] = frag.getId();
return frag;
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE; //To make notifyDataSetChanged() do something
}
}
public class HomeListFragment extends ListFragment
{
...
public static HomeListFragment newInstance(int num)
{
HomeListFragment f = new HomeListFragment();
...
return f;
}
...
如您所见,我的第一次尝试是在整个FragmentPagerAdapter上notifyDataSetChanged,这表明有时会更新数据,但在其他情况下,我得到了一个非法状态异常:onSaveInstanceState之后无法执行此操作
我的第二次尝试涉及尝试调用ListFragment中的更新函数,但getItem中的getId返回0。根据我试过的文件
使用从FragmentManager获取对片段的引用
findFragmentById()或findFragmentByTag()
但我不知道我的碎片的标签或id!我有一个android:id=“@+id/viewpager”用于viewpager,还有一个android:id=“@android:id/list”用于ListFragment布局中的ListView,但我认为这些都没有用
那么,我怎样才能:
a) 一次性安全地更新整个ViewPager(理想情况下是将用户返回到他之前所在的页面)-用户看到视图更改是可以的。
或者更好,
b) 在每个受影响的ListFragment中调用函数以手动更新ListView
任何帮助都将被感激地接受 好的,我想我已经找到了一种方法来执行我自己的问题中的请求b),所以我将为他人的利益而分享。ViewPager中的片段标记的形式为
“android:switcher:ViewPager_ID:INDEX”
,其中ViewPager_ID
是XML布局中的R.ID.ViewPager
,而INDEX是ViewPager中的位置。因此,如果位置已知(例如0),我可以在updateFragments()
中执行:
我不知道这是否是一个有效的方法,但它会做,直到更好的建议 Barkside的答案适用于
FragmentPagerAdapter
,但不适用于FragmentStatePagerAdapter
,因为它不会对传递给FragmentManager
的片段设置标签
使用
FragmentStatePagerAdapter
我们似乎可以通过使用它的实例化项(视图组容器,int位置)
调用。它返回对位置处的片段的引用。如果FragmentStatePagerAdapter
已经持有对相关片段的引用,InstanceItem
只返回对该片段的引用,而不调用getItem()
再次实例化它
所以,假设,我目前正在查看片段50,并希望访问片段49。因为它们很接近,所以#49很有可能已经被实例化了。所以
ViewPager pager = findViewById(R.id.viewpager);
FragmentStatePagerAdapter a = (FragmentStatePagerAdapter) pager.getAdapter();
MyFragment f49 = (MyFragment) a.instantiateItem(pager, 49)
如果您问我,下面页面上的第二个解决方案(跟踪所有“活动”片段页面)更好:
巴克塞德的回答对我来说太粗糙了
您可以跟踪所有“活动”片段页面。在本例中,您将跟踪FragmentStatePagerAdapter中的片段页面,该页面由ViewPager使用
private final SparseArray<Fragment> mPageReferences = new SparseArray<Fragment>();
public Fragment getItem(int index) {
Fragment myFragment = MyFragment.newInstance();
mPageReferences.put(index, myFragment);
return myFragment;
}
。。。当您需要访问当前可见的页面时,您可以调用:
int index = mViewPager.getCurrentItem();
MyAdapter adapter = ((MyAdapter)mViewPager.getAdapter());
MyFragment fragment = adapter.getFragment(index);
。。。其中MyAdapter的getFragment(int)方法如下所示:
public MyFragment getFragment(int key) {
return mPageReferences.get(key);
}
“尝试在每次实例化Fragement时记录标记
public class MPagerAdapter extends FragmentPagerAdapter {
private Map<Integer, String> mFragmentTags;
private FragmentManager mFragmentManager;
public MPagerAdapter(FragmentManager fm) {
super(fm);
mFragmentManager = fm;
mFragmentTags = new HashMap<Integer, String>();
}
@Override
public int getCount() {
return 10;
}
@Override
public Fragment getItem(int position) {
return Fragment.instantiate(mContext, AFragment.class.getName(), null);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Object obj = super.instantiateItem(container, position);
if (obj instanceof Fragment) {
// record the fragment tag here.
Fragment f = (Fragment) obj;
String tag = f.getTag();
mFragmentTags.put(position, tag);
}
return obj;
}
public Fragment getFragment(int position) {
String tag = mFragmentTags.get(position);
if (tag == null)
return null;
return mFragmentManager.findFragmentByTag(tag);
}
}
公共类MPagerAdapter扩展了FragmentPagerAdapter{
私有地图标签;
私人碎片管理器MFFragmentManager;
公共MPagerAdapter(碎片管理器fm){
超级(fm);
MFFragmentManager=fm;
MFFragmentTags=newHashMap();
}
@凌驾
public int getCount(){
返回10;
}
@凌驾
公共片段getItem(int位置){
返回Fragment.instantiate(mContext,affragment.class.getName(),null);
}
@凌驾
公共对象实例化项(视图组容器,int位置){
Object obj=super.instanceItem(容器、位置);
if(obj实例f片段){
//在这里记录片段标记。
片段f=(片段)obj;
String tag=f.getTag();
MFFragmentTags.put(位置,标签);
}
返回obj;
}
公共片段getFragment(int位置){
String tag=MFFragmentTags.get(位置);
if(标记==null)
返回null;
返回mffragmentmanager.findffragmentbytag(tag);
}
}
您可以复制FragmentPagerAdapter
并修改一些源代码,添加getTag()
方法
比如说
public abstract class AppFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = "FragmentPagerAdapter";
private static final boolean DEBUG = false;
private final FragmentManager mFragmentManager;
private FragmentTransaction mCurTransaction = null;
private Fragment mCurrentPrimaryItem = null;
public AppFragmentPagerAdapter(FragmentManager fm) {
mFragmentManager = fm;
}
public abstract Fragment getItem(int position);
@Override
public void startUpdate(ViewGroup container) {
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
final long itemId = getItemId(position);
String name = getTag(position);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
mCurTransaction.attach(fragment);
} else {
fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
mCurTransaction.add(container.getId(), fragment,
getTag(position));
}
if (fragment != mCurrentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
+ " v=" + ((Fragment) object).getView());
mCurTransaction.detach((Fragment) object);
}
@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
mCurrentPrimaryItem.setUserVisibleHint(false);
}
if (fragment != null) {
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
}
mCurrentPrimaryItem = fragment;
}
}
@Override
public void finishUpdate(ViewGroup container) {
if (mCurTransaction != null) {
mCurTransaction.commitAllowingStateLoss();
mCurTransaction = null;
mFragmentManager.executePendingTransactions();
}
}
@Override
public boolean isViewFromObject(View view, Object object) {
return ((Fragment) object).getView() == view;
}
@Override
public Parcelable saveState() {
return null;
}
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
public long getItemId(int position) {
return position;
}
private static String makeFragmentName(int viewId, long id) {
return "android:switcher:" + viewId + ":" + id;
}
protected abstract String getTag(int position);
}
然后扩展它,覆盖这些抽象方法,不必担心Android组的更改
FragmentPageAdapter
未来的源代码
class TimeLinePagerAdapter extends AppFragmentPagerAdapter {
List<Fragment> list = new ArrayList<Fragment>();
public TimeLinePagerAdapter(FragmentManager fm) {
super(fm);
list.add(new FriendsTimeLineFragment());
list.add(new MentionsTimeLineFragment());
list.add(new CommentsTimeLineFragment());
}
public Fragment getItem(int position) {
return list.get(position);
}
@Override
protected String getTag(int position) {
List<String> tagList = new ArrayList<String>();
tagList.add(FriendsTimeLineFragment.class.getName());
tagList.add(MentionsTimeLineFragment.class.getName());
tagList.add(CommentsTimeLineFragment.class.getName());
return tagList.get(position);
}
@Override
public int getCount() {
return list.size();
}
}
类TimeLinePagerAdapter扩展了AppFragmentPagerAdapter{
列表=新的ArrayList();
公共TimeLinePagerAdapter(碎片管理器fm){
超级(fm);
添加(新的FriendsTimeLineFragment());
添加(新提及StimeRefragment());
添加(新的CommentStimeRefragment());
}
公共片段getItem(int位置){
返回列表。获取(位置);
}
@凌驾
受保护字符串getTag(int位置){
List tagList=new ArrayList();
tagList.add(FriendsTimeLineFragment.class.getName());
tagList.add(referentinstimelinefragment.class.getName());
tagList.add(commentStimeRefragment.class.getName());
返回标记列表。获取(位置);
}
@凌驾
public int getCount(){
返回list.size();
}
}
好的,在通过@
public abstract class AppFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = "FragmentPagerAdapter";
private static final boolean DEBUG = false;
private final FragmentManager mFragmentManager;
private FragmentTransaction mCurTransaction = null;
private Fragment mCurrentPrimaryItem = null;
public AppFragmentPagerAdapter(FragmentManager fm) {
mFragmentManager = fm;
}
public abstract Fragment getItem(int position);
@Override
public void startUpdate(ViewGroup container) {
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
final long itemId = getItemId(position);
String name = getTag(position);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
mCurTransaction.attach(fragment);
} else {
fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
mCurTransaction.add(container.getId(), fragment,
getTag(position));
}
if (fragment != mCurrentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
+ " v=" + ((Fragment) object).getView());
mCurTransaction.detach((Fragment) object);
}
@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
mCurrentPrimaryItem.setUserVisibleHint(false);
}
if (fragment != null) {
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
}
mCurrentPrimaryItem = fragment;
}
}
@Override
public void finishUpdate(ViewGroup container) {
if (mCurTransaction != null) {
mCurTransaction.commitAllowingStateLoss();
mCurTransaction = null;
mFragmentManager.executePendingTransactions();
}
}
@Override
public boolean isViewFromObject(View view, Object object) {
return ((Fragment) object).getView() == view;
}
@Override
public Parcelable saveState() {
return null;
}
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
public long getItemId(int position) {
return position;
}
private static String makeFragmentName(int viewId, long id) {
return "android:switcher:" + viewId + ":" + id;
}
protected abstract String getTag(int position);
}
class TimeLinePagerAdapter extends AppFragmentPagerAdapter {
List<Fragment> list = new ArrayList<Fragment>();
public TimeLinePagerAdapter(FragmentManager fm) {
super(fm);
list.add(new FriendsTimeLineFragment());
list.add(new MentionsTimeLineFragment());
list.add(new CommentsTimeLineFragment());
}
public Fragment getItem(int position) {
return list.get(position);
}
@Override
protected String getTag(int position) {
List<String> tagList = new ArrayList<String>();
tagList.add(FriendsTimeLineFragment.class.getName());
tagList.add(MentionsTimeLineFragment.class.getName());
tagList.add(CommentsTimeLineFragment.class.getName());
return tagList.get(position);
}
@Override
public int getCount() {
return list.size();
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// Since the pager fragments don't have known tags or IDs, the only way to persist the
// reference is to use putFragment/getFragment. Remember, we're not persisting the exact
// Fragment instance. This mechanism simply gives us a way to persist access to the
// 'current' fragment instance for the given fragment (which changes across orientation
// changes).
//
// The outcome of all this is that the "Refresh" menu button refreshes the stream across
// orientation changes.
if (mSocialStreamFragment != null) {
getSupportFragmentManager().putFragment(outState, "stream_fragment",
mSocialStreamFragment);
}
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
if (mSocialStreamFragment == null) {
mSocialStreamFragment = (SocialStreamFragment) getSupportFragmentManager()
.getFragment(savedInstanceState, "stream_fragment");
}
}
private class HomePagerAdapter extends FragmentPagerAdapter {
public HomePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return (mMyScheduleFragment = new MyScheduleFragment());
case 1:
return (mExploreFragment = new ExploreFragment());
case 2:
return (mSocialStreamFragment = new SocialStreamFragment());
}
return null;
}
if (mSocialStreamFragment != null) {
mSocialStreamFragment.refresh();
}
public class CustomPagerAdapter extends FragmentStatePagerAdapter{
private Fragment[] fragments;
public CustomPagerAdapter(FragmentManager fm) {
super(fm);
fragments = new Fragment[]{
new FragmentA(),
new FragmentB()
};
}
@Override
public Fragment getItem(int arg0) {
return fragments[arg0];
}
@Override
public int getCount() {
return fragments.length;
}
}
public class MainActivity {
private ViewPager view_pager;
private CustomPagerAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter = new CustomPagerAdapter(getSupportFragmentManager());
view_pager = (ViewPager) findViewById(R.id.pager);
view_pager.setAdapter(adapter);
view_pager.setOnPageChangeListener(this);
...
}
}
int index = view_pager.getCurrentItem();
Fragment currentFragment = adapter.getItem(index);
public void setPrimaryItem(ViewGroup container, int position, Object object) {
if (mCurrentFragment != object) {
mCurrentFragment = (Fragment) object; //Keep reference to object
((MyInterface)mCurrentFragment).viewDidAppear();//Or call a method on the fragment
}
super.setPrimaryItem(container, position, object);
}
public Fragment getCurrentFragment(){
return mCurrentFragment;
}
<FrameLayout android:layout_width="0dp" android:layout_height="0dp" android:visibility="gone" android:id="@+id/fragment_reference">
<View android:layout_width="0dp" android:layout_height="0dp" android:visibility="gone"/>
</FrameLayout>
...
View root = inflater.inflate(R.layout.fragment_page, container, false);
ViewGroup ref = (ViewGroup)root.findViewById(R.id.fragment_reference);
ref.setTag(this);
ref.getChildAt(0).setTag("fragment:" + pageIndex);
return root;
public Fragment getFragment(int pageIndex) {
View w = mViewPager.findViewWithTag("fragment:" + pageIndex);
if (w == null) return null;
View r = (View) w.getParent();
return (Fragment) r.getTag();
}
Bundle b = new Bundle();
b.putInt(Constants.SharedPreferenceKeys.NUM_QUERY_DAYS,numQueryDays);
for(android.support.v4.app.Fragment f:getSupportFragmentManager().getFragments()){
if(f instanceof HomeTermFragment){
((HomeTermFragment) f).restartLoader(b);
}
}