Fragment(碎片)一个简易的新闻应用-Android_碎片实践简易版新闻应用为什么点击按钮之后不显示内容

先看效果

1.首先，要实现上面的效果，就必须得有两个字段，用来显示新闻的标题和内容，所以新建一个新闻类（News）

public class News {
 
    private String title;
    private String content;
 
    public String getTitle() {
        return title;
    }
 
    public void setTitle(String title) {
        this.title = title;
    }
 
    public String getContent() {
        return content;
    }
 
    public void setContent(String content) {
        this.content = content;
    }
}

2.创建用于显示新闻内容的布局

可以看到做左边是可以实现滑动效果的，所以我们新建一个news_title_frag.xml布局来实现它

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
 
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/news_title_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
 
</LinearLayout>

接着再新建一个news_item.xml布局作为上面RecyclerView要展示的内容

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
 
    android:id="@+id/news_title"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:maxLines="2"
    android:ellipsize="end"
    android:textSize="18sp"
    android:paddingLeft="10dp"
    android:paddingRight="10dp"
    android:paddingTop="15dp"
    android:paddingBottom="15dp">
 
</TextView>

右边的布局就如下展示

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 
    android:layout_width="match_parent"
    android:layout_height="match_parent">
 
    <!--新闻内容的布局-->
 
    <LinearLayout
        android:id="@+id/visibility_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:visibility="invisible">
 
        <TextView
            android:gravity="center"
            android:padding="10dp"
            android:textSize="20sp"
            android:id="@+id/news_title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
 
        <View
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="#000000"/>
 
        <TextView
            android:padding="15dp"
            android:textSize="18sp"
            android:id="@+id/news_content"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="0dp" />
 
    </LinearLayout>
 
    <View
        android:layout_width="10dp"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:background="#000" />
 
 
</RelativeLayout>

3.接着在res目录下新建layout-600dp文件夹，在这里面新建一个activity_main.xml文件，并对他添加以下代码，那么我们的布局就已经完成了，接下来就是往布局里添加具体内容了

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/news_title_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
   >
 
    <fragment
        android:layout_weight="1"
        android:id="@+id/news_title_fragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:name="com.example.demo_fragment2.NewsTitleFragment" />
 
    <FrameLayout
        android:id="@+id/news_content_layout"
        android:layout_weight="3"
        android:layout_width="0dp"
        android:layout_height="match_parent">
 
        <fragment
            android:id="@+id/news_content_fragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:name="com.example.demo_fragment2.NewsContentFragment"/>
 
    </FrameLayout>
 
 
 
</LinearLayout>

4.接着分别创建NewsTitleFragment类和NewsContentFragment类继承Fragment

package com.example.demo_fragment2;
 
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
 
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
 
import java.util.ArrayList;
import java.util.List;
 
public class NewsTitleFragment extends Fragment {
 
    //新建一个内部类来作为RecyclerView的适配器
    class NewsAdapter extends RecyclerView.Adapter<NewsAdapter.ViewHolder>{
 
        private List<News> mNewsList;
 
        class ViewHolder extends RecyclerView.ViewHolder{
          TextView newstitleText;
 
          public ViewHolder(View view){
              super(view);
              newstitleText = view.findViewById(R.id.news_title);
          }
        }
        public NewsAdapter(List<News> newsList){
            mNewsList=newsList;
        }
 
        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.new_item, parent, false);
           final ViewHolder holder = new ViewHolder(view);
 
           return holder;
        }
 
        @Override
        public void onBindViewHolder( ViewHolder holder, int position) {
            News news = mNewsList.get(position);
            holder.newstitleText.setText(news.getTitle());
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                        NewsContentFragment fragment= (NewsContentFragment) getFragmentManager()
                                .findFragmentById(R.id.news_content_fragment);
                        fragment.refresh(news.getTitle(),news.getContent());
 
                }
            });
        }
 
        @Override
        public int getItemCount() {
 
            return mNewsList.size();
        }
    }
 
 
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
 
        View view = inflater.inflate(R.layout.news_title_frag,container,false);
 
        RecyclerView news_title_recycler_view = view.findViewById(R.id.news_title_recycler_view);
        LinearLayoutManager linearLayout = new LinearLayoutManager(getActivity());
        news_title_recycler_view.setLayoutManager(linearLayout);
 
        NewsAdapter adapter=new NewsAdapter(getNews());
        news_title_recycler_view.setAdapter(adapter);
 
        return view;
    }
 
    private List<News> getNews(){
       List<News> newsList = new ArrayList<>();
        for (int i = 0; i <= 50; i++) {
            News news = new News();
            news.setTitle("这是一个 news title"+i);
            news.setContent("这是一个 news Content"+i+"****");
            newsList.add(news);
        }
        return newsList;
    }
 
}

package com.example.demo_fragment2;
 
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
 
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
 
public class NewsContentFragment extends Fragment {
 
    private View view;
 
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //绑定外面的布局
        view=inflater.inflate(R.layout.news_content_frag,container,false);
        return view;
    }
 
    //用于将新闻的标题和内容展示
    public void refresh(String newTitle,String newContent){
        View visibility_layout = view.findViewById(R.id.visibility_layout);
        visibility_layout.setVisibility(View.VISIBLE);
 
        TextView title = view.findViewById(R.id.news_title);
        TextView content = view.findViewById(R.id.news_content);
 
        title.setText(newTitle);
        content.setText(newContent);
    }
}

记住，因为我们实现的效果需要平板才能看到