问题

I'm sorry a question that has already been answered in this web, but I can't find same case with mine.

I call lists of multiple columns from `RoomDatabase` for `SetText` in a `ViewPager`, and my question is how to dynamically update `ViewPager` when I delete record. In other questions I've checked, there was a single `TextView` in a `ViewPager`. But in my case, I assign arrays, that I received through bundle, into each `TextView` in `ArrayListFragment` class.

It's so frustrating after searching for what to do after `myAdapter.notifyDataSetChanged()` in delete button.

I will really appreciate your help.


public class FragmentStateLibraryPagerSupport extends Fragment {

    MyAdapter myAdapter;
    ViewPager mPager;
    public List<String> head_array;
    public List<String> desc_array;
    TodoDatabase db;

    @Nullable
    @Override
    public View onCreateView(@NonNull final LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        final View root = inflater.inflate(R.layout.fragment_pager, null);
        Button btn_delete = root.findViewById(R.id.btn_delete);
        btn_delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ArrayListFragment arrayListFragment = new ArrayListFragment();
                String head_array_text = head_array.get(arrayListFragment.return_mNum());
                Log.e("head_array_text ::",  head_array.get(arrayListFragment.return_mNum()));

                TodoDatabase db = Room.databaseBuilder(getContext(), TodoDatabase.class, "todo-db").allowMainThreadQueries().build();
                db.todoDao().deleteRecord(head_array_text);
                myAdapter.notifyDataSetChanged();
            }
        });
        return root;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        db = Room.databaseBuilder(getContext(), TodoDatabase.class, "todo-db").allowMainThreadQueries().build();

        head_array = db.todoDao().getAllHead();
        desc_array = db.todoDao().getAllDesc();

        myAdapter = new MyAdapter(getChildFragmentManager());

        mPager = (ViewPager) view.findViewById(R.id.pager);
        mPager.setAdapter(myAdapter);
    }

    private class MyAdapter extends FragmentStatePagerAdapter {

        public MyAdapter(FragmentManager fm) {
            super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        }

        @NonNull
        @Override
        public Fragment getItem(int position) {
            return ArrayListFragment.newInstance(position, head_array, desc_array);
        }

        @Override
        public int getCount() {
            return head_array.size();
        }

        @Override
        public int getItemPosition(@NonNull Object object) {
            return POSITION_NONE;
        }
    }

    public static class ArrayListFragment extends ListFragment {
        int mNum;
        ArrayList<String> head_array, desc_array;
        Button btn_save;

        public int return_mNum(){
            return mNum;
        }

        static ArrayListFragment newInstance(int num, List<String> head_array, List<String> desc_array) {
            ArrayListFragment arrayListFragment = new ArrayListFragment();
            Bundle bundle = new Bundle();
            bundle.putInt("num", num);
            bundle.putStringArrayList("head_array", (ArrayList<String>) head_array);
            bundle.putStringArrayList("desc_array", (ArrayList<String>) desc_array);
            arrayListFragment.setArguments(bundle);
            return arrayListFragment;
        }

        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            mNum = getArguments() != null ? getArguments().getInt("num") : 1;
            head_array = getArguments().getStringArrayList("head_array");
            desc_array = getArguments().getStringArrayList("desc_array");
        }

        @Nullable
        @Override
        public View onCreateView(@NonNull final LayoutInflater inflater, @Nullable final ViewGroup container, @Nullable Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
            btn_save = v.findViewById(R.id.btn_save);

            final View head_tv = v.findViewById(R.id.head_tv);
            final View desc_tv = v.findViewById(R.id.desc_tv);

            if (head_array.size() == 0) {
                ((TextView) head_tv).setText(R.string.when_no_data_in_DB);
                ((TextView) desc_tv ).setText("");

                btn_save.setVisibility(View.INVISIBLE);
            } else {
                ((TextView) head_tv).setText(head_array.get(mNum));
                ((TextView) desc_tv ).setText(getString(Integer.parseInt(desc_array.get(mNum))));
            }
            return v;
        }
    }
}

英文翻译

I'm sorry a question that has already been answered in this web, but I can't find same case with mine.

I call lists of multiple columns from RoomDatabase for SetText in a ViewPager, and my question is how to dynamically update ViewPager when I delete record. In other questions I've checked, there was a single TextView in a ViewPager. But in my case, I assign arrays, that I received through bundle, into each TextView in ArrayListFragment class.

It's so frustrating after searching for what to do after 'myAdapter.notifyDataSetChanged()' in delete button.

I will really appreciate your help.

public class FragmentStateLibraryPagerSupport extends Fragment {

    MyAdapter myAdapter;
    ViewPager mPager;
    public List&lt;String&gt; head_array;
    public List&lt;String&gt; desc_array;
    TodoDatabase db;

    @Nullable
    @Override
    public View onCreateView(@NonNull final LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        final View root = inflater.inflate( R.layout.fragment_pager, null );
        Button btn_delete = root.findViewById( R.id.btn_delete );
        btn_delete.setOnClickListener( new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ArrayListFragment arrayListFragment = new ArrayListFragment();
                String head_array_text = head_array.get( arrayListFragment.return_mNum() );
                Log.e( &quot;head_array_text ::&quot; ,  head_array.get( arrayListFragment.return_mNum() ));

                TodoDatabase db = Room.databaseBuilder( getContext(), TodoDatabase.class, &quot;todo-db&quot; ).allowMainThreadQueries().build();
                db.todoDao().deleteRecord( head_array_text );
                myAdapter.notifyDataSetChanged();
            }
        } );
        return root;
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated( view, savedInstanceState );
        db = Room.databaseBuilder( getContext(), TodoDatabase.class, &quot;todo-db&quot; ).allowMainThreadQueries().build();

        head_array = db.todoDao().getAllHead();
        desc_array = db.todoDao().getAllDesc();

        myAdapter = new MyAdapter( getChildFragmentManager() );

        mPager = (ViewPager) view.findViewById( R.id.pager );
        mPager.setAdapter( myAdapter );
    }
    private class MyAdapter extends FragmentStatePagerAdapter {

        public MyAdapter(FragmentManager fm) {
            super( fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT );
        }

        @NonNull
        @Override
        public Fragment getItem(int position) {
            return ArrayListFragment.newInstance( position, head_array, desc_array );
        }

        @Override
        public int getCount() {
                return head_array.size();
        }

        @Override
        public int getItemPosition(@NonNull Object object) {
            return POSITION_NONE;
        }
    }

    public static class ArrayListFragment extends ListFragment {
        int mNum;
        ArrayList&lt;String&gt; head_array, desc_array;
        Button btn_save;

        public int return_mNum(){
            return mNum;
        }

        static ArrayListFragment newInstance(int num, List&lt;String&gt; head_array, List&lt;String&gt; desc_array) {
            ArrayListFragment arrayListFragment = new ArrayListFragment();
            Bundle bundle = new Bundle();
            bundle.putInt( &quot;num&quot;, num );
            bundle.putStringArrayList( &quot;head_array&quot;, (ArrayList&lt;String&gt;) head_array );
            bundle.putStringArrayList( &quot;desc_array&quot;, (ArrayList&lt;String&gt;) desc_array );
            arrayListFragment.setArguments( bundle );
            return arrayListFragment;
        }

        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate( savedInstanceState );
            mNum = getArguments() != null ? getArguments().getInt( &quot;num&quot; ) : 1;
            head_array = getArguments().getStringArrayList( &quot;head_array&quot; );
            desc_array = getArguments().getStringArrayList( &quot;desc_array&quot; );
        }

        @Nullable
        @Override
        public View onCreateView(@NonNull final LayoutInflater inflater, @Nullable final ViewGroup container, @Nullable Bundle savedInstanceState) {
            View v = inflater.inflate( R.layout.fragment_pager_list, container, false );
            btn_save = v.findViewById( R.id.btn_save );

            final View head_tv = v.findViewById( R.id.head_tv );
            final View desc_tv = v.findViewById( R.id.desc_tv );

            if (head_array.size() == 0) {
                ((TextView) head_tv).setText( R.string.when_no_data_in_DB );
                ((TextView) desc_tv ).setText( &quot;&quot; );

                btn_save.setVisibility( View.INVISIBLE );
            } else {
                ((TextView) head_tv).setText( head_array.get( mNum ) );
                ((TextView) desc_tv ).setText( getString( Integer.parseInt( desc_array.get( mNum ) ) ) );
            }
            return v;
        }
    }
}

答案1

得分: 0

public class DynamicFragmentPagerAdapter extends PagerAdapter {
    private static final String TAG = "DynamicFragmentPagerAdapter";

    private final FragmentManager fragmentManager;

    public static abstract class FragmentIdentifier implements Parcelable {
        private final String fragmentTag;
        private final Bundle args;

        public FragmentIdentifier(@NonNull String fragmentTag, @Nullable Bundle args) {
            this.fragmentTag = fragmentTag;
            this.args = args;
        }

        protected FragmentIdentifier(Parcel in) {
            fragmentTag = in.readString();
            args = in.readBundle(getClass().getClassLoader());
        }

        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeString(fragmentTag);
            dest.writeBundle(args);
        }

        protected final Fragment newFragment() {
            Fragment fragment = createFragment();
            Bundle oldArgs = fragment.getArguments();
            Bundle newArgs = new Bundle();
            if (oldArgs != null) {
                newArgs.putAll(oldArgs);
            }
            if (args != null) {
                newArgs.putAll(args);
            }
            fragment.setArguments(newArgs);
            return fragment;
        }

        protected abstract Fragment createFragment();
    }

    private ArrayList<FragmentIdentifier> fragmentIdentifiers = new ArrayList<>();

    private FragmentTransaction currentTransaction = null;

    private Fragment currentPrimaryItem = null;

    public DynamicFragmentPagerAdapter(FragmentManager fragmentManager) {
        this.fragmentManager = fragmentManager;
    }

    private int findIndexIfAdded(FragmentIdentifier fragmentIdentifier) {
        for (int i = 0, size = fragmentIdentifiers.size(); i < size; i++) {
            FragmentIdentifier identifier = fragmentIdentifiers.get(i);
            if (identifier.fragmentTag.equals(fragmentIdentifier.fragmentTag)) {
                return i;
            }
        }
        return -1;
    }

    public void addFragment(FragmentIdentifier fragmentIdentifier) {
        if (findIndexIfAdded(fragmentIdentifier) < 0) {
            fragmentIdentifiers.add(fragmentIdentifier);
            notifyDataSetChanged();
        }
    }

    public void removeFragment(FragmentIdentifier fragmentIdentifier) {
        int index = findIndexIfAdded(fragmentIdentifier);
        if (index >= 0) {
            fragmentIdentifiers.remove(index);
            notifyDataSetChanged();
        }
    }

    @Override
    public int getCount() {
        return fragmentIdentifiers.size();
    }

    @Override
    public void startUpdate(@NonNull ViewGroup container) {
        if (container.getId() == View.NO_ID) {
            throw new IllegalStateException("ViewPager with adapter " + this
                    + " requires a view id");
        }
    }

    @SuppressWarnings("ReferenceEquality")
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        if (currentTransaction == null) {
            currentTransaction = fragmentManager.beginTransaction();
        }
        final FragmentIdentifier fragmentIdentifier = fragmentIdentifiers.get(position);
        // Do we already have this fragment?
        final String name = fragmentIdentifier.fragmentTag;
        Fragment fragment = fragmentManager.findFragmentByTag(name);
        if (fragment != null) {
            currentTransaction.attach(fragment);
        } else {
            fragment = fragmentIdentifier.newFragment();
            currentTransaction.add(container.getId(), fragment, fragmentIdentifier.fragmentTag);
        }
        if (fragment != currentPrimaryItem) {
            fragment.setMenuVisibility(false);
            fragment.setUserVisibleHint(false);
        }
        return fragment;
    }

    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        if (currentTransaction == null) {
            currentTransaction = fragmentManager.beginTransaction();
        }
        currentTransaction.detach((Fragment) object);
    }

    @SuppressWarnings("ReferenceEquality")
    @Override
    public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != currentPrimaryItem) {
            if (currentPrimaryItem != null) {
                currentPrimaryItem.setMenuVisibility(false);
                currentPrimaryItem.setUserVisibleHint(false);
            }
            fragment.setMenuVisibility(true);
            fragment.setUserVisibleHint(true);
            currentPrimaryItem = fragment;
        }
    }

    @Override
    public void finishUpdate(@NonNull ViewGroup container) {
        if (currentTransaction != null) {
            currentTransaction.commitNowAllowingStateLoss();
            currentTransaction = null;
        }
    }

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return ((Fragment) object).getView() == view;
    }

    @Override
    public Parcelable saveState() {
        Bundle bundle = new Bundle();
        bundle.putParcelableArrayList("fragmentIdentifiers", fragmentIdentifiers);
        return bundle;
    }

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {
        Bundle bundle = ((Bundle) state);
        bundle.setClassLoader(loader);
        fragmentIdentifiers = bundle.getParcelableArrayList("fragmentIdentifiers");
    }
}

英文翻译

FragmentPagerAdapter is not really intended to support the ability of removing items (dynamic fragment item count).

For that you should use the following code, that tracks identifiers instead of Fragments by position.

public class DynamicFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = &quot;DynamicFragmentPagerAdapter&quot;;

private final FragmentManager fragmentManager;

public static abstract class FragmentIdentifier implements Parcelable {
    private final String fragmentTag;
    private final Bundle args;
  
    public FragmentIdentifier(@NonNull String fragmentTag, @Nullable Bundle args) {
        this.fragmentTag = fragmentTag;
        this.args = args;
    }
  
    protected FragmentIdentifier(Parcel in) {
        fragmentTag = in.readString();
        args = in.readBundle(getClass().getClassLoader());
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(fragmentTag);
        dest.writeBundle(args);
    }
  
    protected final Fragment newFragment() {
        Fragment fragment = createFragment();
        Bundle oldArgs = fragment.getArguments();
        Bundle newArgs = new Bundle();
        if(oldArgs != null) {
            newArgs.putAll(oldArgs);
        }
        if(args != null) {
            newArgs.putAll(args);
        }
        fragment.setArguments(newArgs);
        return fragment;
    }

    protected abstract Fragment createFragment();
}

private ArrayList&lt;FragmentIdentifier&gt; fragmentIdentifiers = new ArrayList&lt;&gt;();

private FragmentTransaction currentTransaction = null;

private Fragment currentPrimaryItem = null;

public DynamicFragmentPagerAdapter(FragmentManager fragmentManager) {
    this.fragmentManager = fragmentManager;
}

private int findIndexIfAdded(FragmentIdentifier fragmentIdentifier) {
    for (int i = 0, size = fragmentIdentifiers.size(); i &lt; size; i++) {
        FragmentIdentifier identifier = fragmentIdentifiers.get(i);
        if (identifier.fragmentTag.equals(fragmentIdentifier.fragmentTag)) {
            return i;
        }
    }
    return -1;
}

public void addFragment(FragmentIdentifier fragmentIdentifier) {
    if (findIndexIfAdded(fragmentIdentifier) &lt; 0) {
        fragmentIdentifiers.add(fragmentIdentifier);
        notifyDataSetChanged();
    }
}

public void removeFragment(FragmentIdentifier fragmentIdentifier) {
    int index = findIndexIfAdded(fragmentIdentifier);
    if (index &gt;= 0) {
        fragmentIdentifiers.remove(index);
        notifyDataSetChanged();
    }
}

@Override
public int getCount() {
    return fragmentIdentifiers.size();
}

@Override
public void startUpdate(@NonNull ViewGroup container) {
    if (container.getId() == View.NO_ID) {
        throw new IllegalStateException(&quot;ViewPager with adapter &quot; + this
                + &quot; requires a view id&quot;);
    }
}

@SuppressWarnings(&quot;ReferenceEquality&quot;)
@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position) {
    if (currentTransaction == null) {
        currentTransaction = fragmentManager.beginTransaction();
    }
    final FragmentIdentifier fragmentIdentifier = fragmentIdentifiers.get(position);
    // Do we already have this fragment?
    final String name = fragmentIdentifier.fragmentTag;
    Fragment fragment = fragmentManager.findFragmentByTag(name);
    if (fragment != null) {
        currentTransaction.attach(fragment);
    } else {
        fragment = fragmentIdentifier.newFragment();
        currentTransaction.add(container.getId(), fragment, fragmentIdentifier.fragmentTag);
    }
    if (fragment != currentPrimaryItem) {
        fragment.setMenuVisibility(false);
        fragment.setUserVisibleHint(false);
    }
    return fragment;
}

@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    if (currentTransaction == null) {
        currentTransaction = fragmentManager.beginTransaction();
    }
    currentTransaction.detach((Fragment) object);
}

@SuppressWarnings(&quot;ReferenceEquality&quot;)
@Override
public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    Fragment fragment = (Fragment) object;
    if (fragment != currentPrimaryItem) {
        if (currentPrimaryItem != null) {
            currentPrimaryItem.setMenuVisibility(false);
            currentPrimaryItem.setUserVisibleHint(false);
        }
        fragment.setMenuVisibility(true);
        fragment.setUserVisibleHint(true);
        currentPrimaryItem = fragment;
    }
}

@Override
public void finishUpdate(@NonNull ViewGroup container) {
    if (currentTransaction != null) {
        currentTransaction.commitNowAllowingStateLoss();
        currentTransaction = null;
    }
}

@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
    return ((Fragment) object).getView() == view;
}

@Override
public Parcelable saveState() {
    Bundle bundle = new Bundle();
    bundle.putParcelableArrayList(&quot;fragmentIdentifiers&quot;, fragmentIdentifiers);
    return bundle;
}

@Override
public void restoreState(Parcelable state, ClassLoader loader) {
    Bundle bundle = ((Bundle)state);
    bundle.setClassLoader(loader);
    fragmentIdentifiers = bundle.getParcelableArrayList(&quot;fragmentIdentifiers&quot;);
}
}

专注分享java语言的经验与见解，让所有开发者获益！

如何在移除片段时动态更新ViewPager

问题

答案1

Go like channels in Java

在低资源环境下使用Apache Cassandra和Go服务器

avatica-go客户端读取Phoenix查询服务器：[驱动程序：连接错误]

向Spring端点发送POST请求，返回状态码400。

Spring Boot控制器从Golang应用程序接收到的重定向请求会被重复执行两次。

可以在不将其读入内存的情况下多次重用HTTP请求体吗？

How to register my go lang microservice in Spring Eureka Service Discovery

在应用程序-go + BDD-java中模拟第三方服务

What is value, reference vs pointer and what these three example used to pass?

Do goroutines and light-weight Java threads mean we never need use thread pools and async code again?

发表评论