我正在尝试使用ViewPager来显示多个片段。目前我只有一个片段,但似乎它从未被实例化。我尝试使用pager.setCurrentItem(0),但适配器中的getItem方法从未被调用。请问在下面的代码中,有人能看出为什么我的片段没有加载吗?
主活动:
主活动:
public class MainActivity extends SherlockFragmentActivity {
MyPagerAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate( savedInstanceState );
setContentView( R.layout.activity_main );
// Create the FragmentPager Adapter and assign it to the viewpager
adapter = new MyPagerAdapter( getSupportFragmentManager(), this );
ViewPager pager = ( ViewPager ) findViewById( R.id.pager );
pager.setAdapter( adapter );
pager.setCurrentItem( 0 );
// Setup the tab page indicator
TabPageIndicator indicator = ( TabPageIndicator ) findViewById( R.id.indicator );
indicator.setViewPager( pager );
}
class MyPagerAdapter extends FragmentStatePagerAdapter {
private SparseArray<Fragment> fragmentPageMap;
public MyPagerAdapter(FragmentManager fm, Activity context) {
super( fm );
fragmentPageMap = new SparseArray<Fragment>();
}
@Override
public Fragment getItem(int index) {
switch ( index ) {
case 0:
if ( fragmentPageMap.get( index ) != null ) {
SherlockListFragment scheduleFragment = ScheduleListFragment.newInstance();
fragmentPageMap.put( index, scheduleFragment );
return scheduleFragment;
} else {
return fragmentPageMap.get( index );
}
default:
return null;
}
}
/*@Override
public void destroyItem(View container, int index, Object object) {
super.destroyItem( container, index, object );
fragmentPageMap.remove( index );
}*/
@Override
public CharSequence getPageTitle(int index) {
return ( ( ViewPagerPage ) fragmentPageMap.get( index ) ).getTitle();
}
@Override
public int getCount() {
return fragmentPageMap.size();
}
}
public interface ViewPagerPage {
String getTitle();
}
主活动布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<com.viewpagerindicator.TabPageIndicator
android:id="@+id/indicator"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textStyle="bold" />
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" />
</LinearLayout>
日程列表碎片
public class ScheduleListFragment extends SherlockListFragment implements ViewPagerPage {
private ScheduleAdapter adapter;
private final String TITLE = "Schedule";
public static ScheduleListFragment newInstance() {
ScheduleListFragment newFrag = new ScheduleListFragment();
Bundle args = new Bundle();
newFrag.setArguments( args );
return newFrag;
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate( R.layout.fragment_schedule_list, null );
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate( R.menu.fragment_schedule_list, menu );
}
// Container Activity must implement this interface
public interface OnAddItemClickedListener {
public void onAddItemClicked();
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch ( item.getItemId() ) {
case R.id.add_item:
Intent myIntent = new Intent( getActivity(), AddScheduleItemActivity.class );
startActivityForResult( myIntent, 1 );
return true;
default:
return super.onOptionsItemSelected( item );
}
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated( savedInstanceState );
setHasOptionsMenu( true );
adapter = new ScheduleAdapter( getActivity() );
setListAdapter( adapter );
}
private class SampleItem {
public String tag;
public int iconRes;
public SampleItem(String tag, int iconRes) {
this.tag = tag;
this.iconRes = iconRes;
}
}
public class ScheduleAdapter extends ArrayAdapter<SampleItem> {
public ScheduleAdapter(Context context) {
super( context, 0 );
}
public View getView(int position, View convertView, ViewGroup parent) {
if ( convertView == null ) {
convertView = LayoutInflater.from( getContext() ).inflate( R.layout.results_list_row, null );
}
ImageView icon = ( ImageView ) convertView.findViewById( R.id.row_icon );
icon.setImageResource( getItem( position ).iconRes );
TextView title = ( TextView ) convertView.findViewById( R.id.row_title );
title.setText( getItem( position ).tag );
return convertView;
}
}
@Override
public String getTitle() {
return TITLE;
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if ( resultCode == android.app.Activity.RESULT_OK ) {
String name = ( String ) data.getExtras().get( "TEXT" );
Toast.makeText( getActivity(), name, Toast.LENGTH_LONG ).show();
}
}
片段布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
谢谢,Nathan
目前的解决方案:
更改适配器构造函数以初始化第一个片段并将其添加到内部地图中。是否有人认为这样做有问题或者有任何可以改进以上代码的方法?谢谢!
public MyPagerAdapter(FragmentManager fm, Activity context) {
super( fm );
fragmentPageMap = new SparseArray<Fragment>();
SherlockListFragment scheduleFragment = ScheduleListFragment.newInstance();
fragmentPageMap.put( 0, scheduleFragment );
}
fragmentPageMap
是在构造函数中创建的,并且在调用getItem(index)
之前,getCount()
被调用,此时fragmentPageMap
为空。您可以在调试器中检查这一点。 - rubenlop88