我正在尝试使我的标签式活动内容动态更改，取决于其他标签中的用户选择。
所有标签使用相同的片段。只有视图中的内容应该更改（在本例中为ListView）
现在主要的问题是当我做出选择时（单击ListView中的某一行），下一个选项卡会显示所有内容，而不是根据我在上一个选项卡中的选择过滤数据，但是当我点击时一个非邻居选项卡，然后返回，选项卡被过滤，就像我想要的那样。
根据我的理解，活动会加载当前选项卡的邻居选项卡，即使这些选项卡没有聚焦，这也是我获得默认结果的原因。
简化事情：
然后我从ListView中选择一行，焦点自动转到下一个标签。
listView将向我显示默认语句，就像我没有选择任何内容一样。但是，如果我将焦点移动到第四个选项卡，然后再次返回到第二个选项卡，listView将按照我想要的方式进行过滤
这是我的代码
public class Catalog_actbartabs extends AppCompatActivity {
/**
* 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.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
public static String PACKAGE_NAME;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_catalog_actbartabs);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
PACKAGE_NAME = getApplicationContext().getPackageName();
}
public void setCurrentItem(int item, boolean smoothScroll) {
mViewPager.setCurrentItem(item, smoothScroll);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_catalog_actbartabs, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
protected ClogListAdapter2 clogListAdapter2;
protected ArrayList<String[]> stringArrayList;
protected static String topic = null;
protected static String rName = null;
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
private static final String EXTRA_ITEM_INFO = "com.dstudio.dvir.EXTRA_ITEM_INFO";
public PlaceholderFragment() {
}
/**
* 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;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView;
rootView = inflater.inflate(R.layout.fragment_catalog, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
try {
if (getArguments().getInt(ARG_SECTION_NUMBER) == 1)
stringArrayList = Utils.getNamesList(super.getContext());
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 2)
stringArrayList = Utils.getTopicsList(super.getContext(), rName);
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 3)
stringArrayList = Utils.getClassesList(super.getContext(), rName, topic);
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 4)
stringArrayList = Utils.getFilesList(super.getContext());
} catch (Throwable t) {
Toast.makeText(super.getContext(), "Exception: " + t.toString(), Toast.LENGTH_LONG).show();
}
if (savedInstanceState != null) {
String[] values = savedInstanceState.getStringArray("myKey");
if (values != null) {
stringArrayList = ClogListAdapter2.bmListFromArray(values);
}
} else if (stringArrayList == null) {
stringArrayList = new ArrayList<String[]>();
}
clogListAdapter2 = new ClogListAdapter2(super.getContext(), stringArrayList, getArguments().getInt(ARG_SECTION_NUMBER));
ListView listV = (ListView) rootView.findViewById(R.id.listView);
listV.setAdapter(clogListAdapter2);
listV.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if (getArguments().getInt(ARG_SECTION_NUMBER) == 1) {
if (clogListAdapter2.getItem(position)[0].equals("All"))
rName = null;
else rName = clogListAdapter2.getItem(position)[0];
topic = null;
} else if (getArguments().getInt(ARG_SECTION_NUMBER) == 2) {
if (clogListAdapter2.getItem(position)[0].equals("All"))
topic = null;
else topic = clogListAdapter2.getItem(position)[0];
} else if (getArguments().getInt(ARG_SECTION_NUMBER) == 4) {
Intent intent = new Intent(parent.getContext(), AudioPlayerActivity.class);
intent.putExtra(EXTRA_ITEM_INFO, clogListAdapter2.getItem(position));
startActivityForResult(intent, 1);
}
((Catalog_actbartabs) getActivity()).setCurrentItem(getArguments().getInt(ARG_SECTION_NUMBER), true);
}
});
return rootView;
}
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 4 total pages.
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "page 1";
case 1:
return "page 2";
case 2:
return "page 3";
case 3:
return "page 4";
}
return null;
}
}
}
我将var _hasLoadedOnce= false;添加到PlaceholderFragment类的其他变量中：
public static class PlaceholderFragment extends Fragment {
protected ClogListAdapter2 clogListAdapter2;
protected ArrayList<String[]> stringArrayList;
protected View rootView;
protected static String topic = null;
protected static String rName = null;
private boolean _hasLoadedOnce= false;
//Rest of the code
}
现在所有数据设置代码都在setUserVisibleHint()内，而不更改_hasLoadedOnce所以它看起来像这样：
@Override
public void setUserVisibleHint(boolean isFragmentVisible_) {
super.setUserVisibleHint(true);
if (this.isVisible()) {
// we check that the fragment is becoming visible
if (isFragmentVisible_ && !_hasLoadedOnce) {
Log.i("visable: ", getArguments().getInt(ARG_SECTION_NUMBER)+"");
try {
if (getArguments().getInt(ARG_SECTION_NUMBER) == 1)
stringArrayList = Utils.getNamesList(super.getContext());
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 2)
stringArrayList = Utils.getTopicsList(super.getContext(), rName);
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 3)
stringArrayList = Utils.getClassesList(super.getContext(), rName, topic);
else if (getArguments().getInt(ARG_SECTION_NUMBER) == 4)
stringArrayList = Utils.getFilesList(super.getContext());
} catch (Throwable t) {
Toast.makeText(super.getContext(), "Exception: " + t.toString(), Toast.LENGTH_LONG).show();
}
clogListAdapter2 = new ClogListAdapter2(super.getContext(), stringArrayList, getArguments().getInt(ARG_SECTION_NUMBER));
ListView listV = (ListView) rootView.findViewById(R.id.listView);
listV.setAdapter(clogListAdapter2);
listV.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// TODO: 23/12/2016 remember to also give the needed info to get the asked next category
if (getArguments().getInt(ARG_SECTION_NUMBER) == 1) {
if (clogListAdapter2.getItem(position)[0].equals("All"))
rName = null;
else rName = clogListAdapter2.getItem(position)[0];
topic = null;
} else if (getArguments().getInt(ARG_SECTION_NUMBER) == 2) {
if (clogListAdapter2.getItem(position)[0].equals("All"))
topic = null;
else topic = clogListAdapter2.getItem(position)[0];
} else if (getArguments().getInt(ARG_SECTION_NUMBER) == 4) {
Intent intent = new Intent(parent.getContext(), AudioPlayerActivity.class);
intent.putExtra(EXTRA_ITEM_INFO, clogListAdapter2.getItem(position));
startActivityForResult(intent, 1);
}
((Catalog_actbartabs) getActivity()).setCurrentItem(getArguments().getInt(ARG_SECTION_NUMBER), true);
}
});
//Notify that _hasLoadedOnce = true; is now gone
}
}
}
我还在活动的mViewPager.setOffscreenPageLimit(3);中添加了行onCreate()，因为如果我在第一次过滤后选择直接转到第四个标签，则不会对其进行过滤，这样活动就会过滤它正确。
答案 0 :(得分：0)
这是ViewPager的默认行为。要仅加载单个标签，请使用：
mViewPager.setOffscreenPageLimit(1);
如果这不起作用，那么你必须创建自己的ViewPager子类并覆盖以下方法：
private boolean _hasLoadedOnce= false; // your boolean field
@Override
public void setUserVisibleHint(boolean isFragmentVisible_) {
super.setUserVisibleHint(true);
if (this.isVisible()) {
// we check that the fragment is becoming visible
if (isFragmentVisible_ && !_hasLoadedOnce) {
//your code here
_hasLoadedOnce = true;
}
}
}