如何将值从 ArrayList 传递到另一个 Fragment

Question

我有一个RecyclerView，它可以模拟新闻源。我希望，如果您单击RecyclerView 的一个项目，该项目的文本会显示在另一个Fragment's TextView 中。新闻源中的帖子文本保存在ArrayList 中。我已经尝试了很多小时将ArrayList 的值传递给应该显示的Fragment 中的TextView，但我真的不明白。这是我的代码：

RecyclerView 适配器

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.TextView;


public class RvAdapterKlasseTalkFragment extends RecyclerView.Adapter<RvAdapterKlasseTalkFragment.ViewHolderKlasseTalkFragment>{


    public static class ViewHolderKlasseTalkFragment extends RecyclerView.ViewHolder{

        TextView userName;
        TextView postText;
        // IMAGE FÜR DEN POST FEHLT!!!!!!!!!
        TextView zeit;
        TextView anzahlKommentare;
        TextView anzahlLikes;
        ImageButton moreButton;

        TextView loeschen;

        public  ViewHolderKlasseTalkFragment (View itemView){
            super(itemView);
            userName = (TextView) itemView.findViewById(R.id.userName);
            postText = (TextView) itemView.findViewById(R.id.postText);
            zeit = (TextView) itemView.findViewById(R.id.zeit);
            anzahlKommentare = (TextView) itemView.findViewById(R.id.anzahlKommentare);
            anzahlLikes = (TextView) itemView.findViewById(R.id.anzahlLikes);
            moreButton = (ImageButton) itemView.findViewById(R.id.moreButton);
            loeschen = (TextView) itemView.findViewById(R.id.loeschen);
        }
    }

    @Override
    public ViewHolderKlasseTalkFragment onCreateViewHolder(ViewGroup viewGroup, int viewType) {

        View itemView1 = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.iten_layout_post, null);
        return new ViewHolderKlasseTalkFragment(itemView1);
    }

    @Override
    public void onBindViewHolder(final ViewHolderKlasseTalkFragment viewHolderKlasse,final int i) {
        viewHolderKlasse.userName.setText(TalkscreenFragment.userName);
        viewHolderKlasse.userName.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(v.getContext(), ProfilePopUp.class);
                v.getContext().startActivity(intent);
            }
        });
        viewHolderKlasse.postText.setText(TalkscreenFragment.postText.get(i));
        viewHolderKlasse.zeit.setText(TalkscreenFragment.currentDateTimeString);
        viewHolderKlasse.anzahlKommentare.setText(TalkscreenFragment.anzahlKommentare);
        viewHolderKlasse.anzahlLikes.setText(TalkscreenFragment.anzahlLikes);
        viewHolderKlasse.moreButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(v.getContext(), ContextMenuPopUp.class);
                v.getContext().startActivity(intent);
            }
        });


    }

    @Override
    public int getItemCount() {
        return TalkscreenFragment.postText.size();
    }
}

使用 ArrayList 和 RecyclerView 的活动

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageButton;
import android.widget.TextView;

import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;

public class Talkscreen extends AppCompatActivity {

    public static LinearLayoutManager rvLayoutManagerTalkFragment;
    public static RecyclerView recyclerViewTalkFragment;
    public static RecyclerView.Adapter rvadapterTalkFragment;

    public static ArrayList<String> postText;

    public static String userName = "Benutzer 1";
    public static String anzahlKommentare = "1.243";
    public static String anzahlLikes = "15540";
    public static String currentDateTimeString;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_talkscreen);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getBaseContext(), PostScreen.class);
                startActivity(intent);
            }
        });

        TextView meineaktivitaeten = (TextView) findViewById(R.id.meineAktivitaeten);
        meineaktivitaeten.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getBaseContext(), MeineAktivitaeten.class);
                startActivity(intent);
            }
        });

        postText = new ArrayList<>();
        postText.addAll(Arrays.asList("TEXT 1",
                "TEXT 2",
                "TEXT 3",
                "TEXT 4"));

        currentDateTimeString = DateFormat.getTimeInstance().format(new Date());

        recyclerViewTalkFragment = (RecyclerView) findViewById(R.id.recycleviewTalkFragment);
        rvLayoutManagerTalkFragment = new LinearLayoutManager(this);
        recyclerViewTalkFragment.setLayoutManager(rvLayoutManagerTalkFragment);
        rvadapterTalkFragment = new RvAdapterKlasseTalkFragment();
        recyclerViewTalkFragment.setAdapter(rvadapterTalkFragment);


    }

    @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_talkscreen, 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.einstellungen) {
            startActivity(new Intent(this, Einstellungen.class));
        }


        if (id == R.id.information) {
            startActivity(new Intent(this, Information.class));
        }



        return super.onOptionsItemSelected(item);
    }
}

应该显示 ArrayList 值的片段

import android.os.Bundle;
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.
 */
public class MeinePosts extends Fragment {


    public static MeinePosts newInstance(){
        MeinePosts fragment = new MeinePosts();
        return fragment;
    }

    public MeinePosts() {
    }

    TextView postedText;



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View rootView = inflater.inflate(R.layout.fragment_meine_posts, container, false);

        postedText = (TextView) rootView.findViewById(R.id.postTextMeinePosts);


        return rootView;

    }


}

感谢您的帮助！

Answer 1

在

片段：

import android.os.Bundle;
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.
 */
public class MeinePosts extends Fragment {

    private ArrayList<String> fragmentList;

    public static MeinePosts newInstance(){
        MeinePosts fragment = new MeinePosts();
        return fragment;
    }

    /*HERE YOU RECIVE PARAMETER ARRAYLIST*/
    public MeinePosts(ArrayList<String> myList) {
        /*Now from here you can set the arraylist
          to other...  it can be access from any method
          if you set on class*/
          fragmentList = myList;
    }

    TextView postedText;



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View rootView = inflater.inflate(R.layout.fragment_meine_posts, container, false);

        postedText = (TextView) rootView.findViewById(R.id.postTextMeinePosts);


        return rootView;

    }


}

Answer 2

Android 中fragment 间通信的最佳方式是通过两个 Fragment 中的接口，其中 Activity 作为中间人。 为此，您必须为您希望能够向活动发送信息的片段声明一个接口。

首先在您的 Fragment RvAdapterKlasseTalkFragment 中执行此操作： 公共类 RvAdapterKlasseTalkFragment 扩展 RecyclerView.Adapter {

    // Declare this interface
    public Interface AdapterInterface() {
        public void sendValueToActivity(String value);
    }

    // Create an object to reference the activity that implements the previous interface (Talkscreen)
    AdapterInterface activityConnection;

    // in your onclick call the interface
    @Override
    public void onBindViewHolder(final ViewHolderKlasseTalkFragment viewHolderKlasse,final int i) {
        viewHolderKlasse.userName.setText(TalkscreenFragment.userName);
        viewHolderKlasse.userName.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                connectedActivity.sendValueToActivity(myvalue);
            }
        });

    // here is where you link the interface to the activity and you can openly exchange information now
     @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        try {
            activityConnection = (AdapterInterface) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString() + " must implement AdapterInterface");
        }
    }

}

在您的 MeineFragment 中设置一个方法，您可以从 Activity 中直接引用此类的片段对象调用该方法：

public class MeinePosts extends Fragment {

    // add this method to your MeinePosts fragment
    public void setTextViewValue(String value) {
        postedText.setText(value);
    }

}

最后在你的 Activity 中实现第一个片段中声明的接口：

public class Talkscreen extends AppCompatActivity implements MyInterface {
    @Override
    public void sendValueToActivity(String value) {
        // here invoque a method in the second fragment for example
        AdapterFragment.setTextViewValue(value);
    }
}

如果您还需要将信息从第二个片段发送到第一个片段，您还需要实现相同的步骤（在第二个片段中声明接口，在活动中实现它，在片段中链接它，然后在活动在第一个片段中调用一个新方法来做你想做的事）

如果您还需要更多信息，我在 Github 中有这个项目进行片段间通信。 https://github.com/isaacurbina/FragmentsExercise

希望对你有帮助！亲切的问候！

Answer 3

首先，我犯了一个可怕的错误。 MeinePost Fragment 中初始化的TextView 指的是RelativeLayout 而不是TextView。

我发现了一种相对简单的方法来实现我想要的。这可能不是最好的解决方案，但它对我有用：

第一步：

RecyclerView 适配器

viewHolderKlasse.postText.setText(Talkscreen.postText.get(i));
        viewHolderKlasse.postText.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(v.getContext(), AngeklickterPost.class);
                intent.putExtra("data", Talkscreen.postText.get(i)); //data is a string variable holding some value.
                v.getContext().startActivity(intent);
            }
        });

第二步：我需要为我的意图创建一个新 Activity

AngeklickterPost 活动

package com.appmac.ron.gamestalk;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.widget.TextView;

public class AngeklickterPost extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_angeklickter_post);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        String data = getIntent().getStringExtra("data");
        TextView postTextPosted = (TextView) findViewById(R.id.postTextPosted);
        postTextPosted.setText(data);
    }

}

希望这篇文章对可能遇到同样问题的人有所帮助。如果有什么我可以做得更好的，请评论！