不同片段上的相同浮动操作按钮

Question

我使用FragmentStatePagerAdapter 来显示片段列表，每个片段都有一个浮动操作按钮。当我在片段之间滑动切换时，浮动操作按钮也会发生变化，所以我的问题是，当我在片段之间滑动时，是否可以只保持浮动操作按钮不改变？

活动代码

package client.tclient.com.client;

import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class FollowingActivity extends AppCompatActivity implements TweetFragment.OnFragmentInteractionListener{

    ListView homeList;
    SwipeRefreshLayout mySwipeRefreshLayout;
    FloatingActionButton fab;

    MyPagerAdapter mPagerAdapter;
    ViewPager mviewPager;
    private List<Fragment> listaFragments;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_following);
        getSupportActionBar().setDisplayShowTitleEnabled(false);


        listaFragments = new ArrayList<Fragment>();
        listaFragments.add(TweetFragment.newInstance(1));
        listaFragments.add(TweetFragment.newInstance(2));
        listaFragments.add(TweetFragment.newInstance(3));


        // Creamos nuestro Adapter
        mPagerAdapter = new MyPagerAdapter(getSupportFragmentManager(),
                listaFragments);

        // Instanciamos nuestro ViewPager
        mviewPager = (ViewPager) findViewById(R.id.viewPager);

        // Establecemos el Adapter
        mviewPager.setAdapter(mPagerAdapter);

    }

    @Override
    public void onFragmentInteraction(Uri uri) {

    }

}

片段代码

package client.tclient.com.client;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link TweetFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link TweetFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class TweetFragment extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    public static final TweetFragment newInstance(long id){
        TweetFragment tf = new TweetFragment();
        Bundle bundle = new Bundle(1);
        bundle.putLong("TWEET_ID",id);
        tf.setArguments(bundle);

        return tf;
    }
    public TweetFragment() {
        // Required empty public constructor
    }


    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment TweetFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static TweetFragment newInstance(String param1, String param2) {
        TweetFragment fragment = new TweetFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View inflate = inflater.inflate(R.layout.fragment_tweet, container, false);
        TextView text =(TextView) inflate.findViewById(R.id.text);
        text.setText(Long.toString(getArguments().getLong("TWEET_ID")));

        FloatingActionButton fab = (FloatingActionButton) inflate.findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Se presionó el FAB", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        return inflate;
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p/>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

Answer 1

当我在片段之间滑动时，是否可以只保持一个浮动操作按钮不改变？

这绝对是可能的，只需通过 XML 在您的 ViewPager 顶部的活动布局中创建一个 FloatingActionButton。您可以通过CoordinatorLayout 实现这一目标。

有很多在活动中使用操作按钮的示例，我认为在您的情况下，唯一的区别是您使用 ViewPager 而不是 ImageView，这对 FAB 实现没有影响。另外，从片段的布局中删除按钮，因为您不需要在每个页面上显示它。

实现布局后，将onClickListener 添加到活动中的该按钮。如果您需要在ViewPager 中使用当前片段中的一些数据，您可以通过调用mviewPager.getCurrentItem() 来获取它的索引，所以这应该不是问题。

如果您有更具体的问题，请尽可能缩小范围，以便我们以更准确的方式回答。