Android第一行代码之制作简易版新闻应用

 1 public class News {
 2     private String title;//新闻标题
 3     private String content;//新闻内容
 4 
 5     public String getTitle() {
 6         return title;
 7     }
 8 
 9     public void setTitle(String title) {
10         this.title = title;
11     }
12 
13     public String getContent() {
14         return content;
15     }
16 
17     public void setContent(String content) {
18         this.content = content;
19     }
20 
21 
22 }

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent">
 5 
 6     <LinearLayout
 7         android:id="@+id/visibility_layout"
 8         android:layout_width="match_parent"
 9         android:layout_height="match_parent"
10         android:orientation="vertical"
11         android:visibility="invisible">
12 
13         <TextView
14             android:id="@+id/news_title"
15             android:layout_width="match_parent"
16             android:layout_height="wrap_content"
17             android:gravity="center"
18             android:padding="10dp"
19             android:textSize="20sp"/>
20         <View
21             android:layout_width="match_parent"
22             android:layout_height="1dp"
23             android:background="#000"/>
24         <TextView
25             android:id="@+id/news_content"
26             android:layout_width="match_parent"
27             android:layout_height="0dp"
28             android:layout_weight="1"
29             android:padding="15dp"
30             android:textSize="18sp"/>
31     </LinearLayout>
32     <View
33         android:layout_width="match_parent"
34         android:layout_height="1dp"
35         android:layout_alignParentLeft="true"
36         android:background="#000"/>
37 
38 </RelativeLayout>

 1 package com.example.fragmentbestpractice;
 2 
 3 import android.os.Bundle;
 4 import android.view.LayoutInflater;
 5 import android.view.View;
 6 import android.view.ViewGroup;
 7 import android.widget.TextView;
 8 
 9 import androidx.annotation.NonNull;
10 import androidx.annotation.Nullable;
11 import androidx.appcompat.app.AppCompatActivity;
12 import androidx.fragment.app.Fragment;
13 
14 public class NewsContentFragment extends Fragment {
15     private View view;
16 
17     @Nullable
18     @Override//加载news_content_frag布局
19     public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
20         view=inflater.inflate(R.layout.news_content_frag,container,false);
21         return view;
22     }
23     public void refresh(String newsTitle,String newsContent){
24         View visibilityLayout=view.findViewById(R.id.visibility_layout);//获取新闻布局
25         visibilityLayout.setVisibility(View.VISIBLE);//将新闻布局设置成可见
26         TextView newsTitleText=(TextView)view.findViewById(R.id.news_title);//获取新闻标题的控件
27         TextView newsContentText=(TextView)view.findViewById(R.id.news_content);//获取新闻内容的控件
28         newsTitleText.setText(newsTitle); //刷新新闻的标题
29         newsContentText.setText(newsContent);//刷新新闻的内容
30     }
31 }

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:orientation="vertical"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent">
 6     <fragment
 7         android:id="@+id/news_content_fragment"
 8         android:name="com.example.fragmentbestpractice.NewsContentFragment"
 9         android:layout_width="match_parent"
10         android:layout_height="match_parent"/>
11 </LinearLayout>

 1 package com.example.fragmentbestpractice;
 2 
 3 import androidx.appcompat.app.AppCompatActivity;
 4 
 5 import android.content.Context;
 6 import android.content.Intent;
 7 import android.os.Bundle;
 8 
 9 public class NewsContentActivity extends AppCompatActivity {
10     public static void actionStart(Context context,String newsTitle,String newsContent){
11         Intent intent=new Intent(context,NewsContentActivity.class);
12         intent.putExtra("news_title",newsTitle);
13         intent.putExtra("news_content",newsContent);
14         context.startActivity(intent);
15     }
16     @Override
17     protected void onCreate(Bundle savedInstanceState) {
18         super.onCreate(savedInstanceState);
19         setContentView(R.layout.news_content);
20         String newsTitle=getIntent().getStringExtra("news_title");//获取传入的新闻标题
21         String newsContent=getIntent().getStringExtra("news_content");//获取传入的新闻内容
22         NewsContentFragment newsContentFragment=(NewsContentFragment)getSupportFragmentManager()
23                 .findFragmentById(R.id.news_content_fragment);
24         newsContentFragment.refresh(newsTitle,newsContent);//刷新NewsContentFragment界面
25     }
26 }

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:orientation="vertical"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent">
 6 
 7     <androidx.recyclerview.widget.RecyclerView
 8         android:id="@+id/news_title_recycler_view"
 9         android:layout_width="match_parent"
10         android:layout_height="match_parent"/>
11 
12 </LinearLayout>

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <!--这是标题列表里的每个子项，即每个新闻标题-->
 3 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
 4     android:id="@+id/news_title"
 5     android:layout_width="match_parent"
 6     android:layout_height="wrap_content"
 7     android:maxLines="1"
 8     android:ellipsize="end"
 9     android:textSize="18sp"
10     android:paddingLeft="10dp"
11     android:paddingRight="10dp"
12     android:paddingTop="15dp"
13     android:paddingBottom="15dp">
14 
15 </TextView>

  1 package com.example.fragmentbestpractice;
  2 
  3 import android.os.Bundle;
  4 import android.view.LayoutInflater;
  5 import android.view.View;
  6 import android.view.ViewGroup;
  7 import android.widget.TextView;
  8 
  9 import androidx.annotation.NonNull;
 10 import androidx.annotation.Nullable;
 11 import androidx.fragment.app.Fragment;
 12 import androidx.recyclerview.widget.LinearLayoutManager;
 13 import androidx.recyclerview.widget.RecyclerView;
 14 
 15 import java.util.ArrayList;
 16 import java.util.List;
 17 import java.util.Random;
 18 
 19 /**
 20  * 展示新闻列表
 21  */
 22 public class NewsTitleFragment extends Fragment {
 23     private boolean isTwopane;//判断是否显示双页
 24 
 25     @Nullable
 26     @Override
 27     public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
 28         View view=inflater.inflate(R.layout.news_title_frag,container,false); 34         return view;
 35     }
 57     @Override
 58     public void onActivityCreated(@Nullable Bundle savedInstanceState) {
 59         super.onActivityCreated(savedInstanceState);
 60         if(getActivity().findViewById(R.id.news_content_layout)!=null){
 61             isTwopane=true;//可以找到news_content_layout布局时，为双页模式
 62         }else{
 63             isTwopane=false;//找不到news_content_layout布局时，为单页模式
 64         }
 65     }
109     }
110 }

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <!--在单页模式下，只显示一个新闻标题碎片-->
 3 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 4     android:id="@+id/activity_main"
 5     android:layout_width="match_parent"
 6     android:layout_height="match_parent"
 7     >
 8 
 9     <fragment
10         android:id="@+id/news_title_fragment"
11         android:name="com.example.fragmentbestpractice.NewsTitleFragment"
12         android:layout_width="match_parent"
13         android:layout_height="match_parent"/>
14 
15 </FrameLayout>

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     android:orientation="horizontal"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent">
 5 
 6     <fragment
 7         android:id="@+id/news_title_fragment"
 8         android:name="com.example.fragmentbestpractice.NewsTitleFragment"
 9         android:layout_width="0dp"
10         android:layout_height="match_parent"
11         android:layout_weight="1"/>
12     <FrameLayout
13         android:id="@+id/news_content_layout"
14         android:layout_width="0dp"
15         android:layout_height="match_parent"
16         android:layout_weight="3">
17         <fragment
18             android:id="@+id/news_content_fragment"
19             android:name="com.example.fragmentbestpractice.NewsContentFragment"
20             android:layout_width="match_parent"
21             android:layout_height="match_parent"/>
22 
23     </FrameLayout>
24 
25 
26 </LinearLayout>

package com.example.fragmentbestpractice;

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;
import java.util.Random;

/**
 * 展示新闻列表
 */
public class NewsTitleFragment extends Fragment {
    private boolean isTwopane;//判断是否显示双页

    @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 newsTitleRecyclerView=(RecyclerView)view.findViewById(R.id.news_title_recycler_view);
        LinearLayoutManager layoutManager=new LinearLayoutManager((getActivity()));
        newsTitleRecyclerView.setLayoutManager(layoutManager);
        NewsAdapter adapter=new NewsAdapter(getNews());
        newsTitleRecyclerView.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("This is news title "+i);
            news.setContent(getRandomLengthContent("This is news content "+i+"."));
            newsList.add(news);
        }
        return newsList;
    }
    private  String getRandomLengthContent(String content){
        Random random=new Random();
        int length=random.nextInt(20)+1;
        StringBuilder builder=new StringBuilder();
        for(int i=0;i<length;i++){
            builder.append(content);
        }
        return builder.toString();
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if(getActivity().findViewById(R.id.news_content_layout)!=null){
            isTwopane=true;//可以找到news_content_layout布局时，为双页模式
        }else{
            isTwopane=false;//找不到news_content_layout布局时，为单页模式
        }
    }
    class NewsAdapter extends RecyclerView.Adapter<NewsAdapter.ViewHolder>{
        private List<News> mNewsList;
        class ViewHolder extends RecyclerView.ViewHolder{
            TextView newsTitleText;
            //构造器传入一个View参数，View参数就是RecyclerView子项的最外层布局
            public ViewHolder(View view){
                super(view);
                newsTitleText=(TextView)view.findViewById(R.id.news_title);
            }
        }

        //NewsAdapter内部类的构造器，这个方法用于将要展示在界面的数据源传进来，并赋值给一个全局变量mFruitAdapter
        public NewsAdapter(List<News> newsList){
            mNewsList=newsList;
        }

        @NonNull
        @Override
        //因为NewsAdapter是继承RecyclerView.Adapeter的，所以必须重写以下三个方法
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view=LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item,parent,false);//加载子项布局
            final ViewHolder holder=new ViewHolder(view);//将加载的布局传入到ViewHolder类构造函数中
            view.setOnClickListener(new View.OnClickListener(){
                @Override
                public void onClick(View v) {//当用户点击每一个新闻标题时，就会显示新闻内容
                    News news=mNewsList.get(holder.getAdapterPosition());
                    if(isTwopane){//如果是双页模式，则刷新NewsContentFragment的内容
                        NewsContentFragment newsContentFragment=(NewsContentFragment)getFragmentManager().findFragmentById(R.id.news_content_fragment);
                        newsContentFragment.refresh(news.getTitle(),news.getContent());
                    }else{//如果是单页模式，直接启动NewsContentActivity
                        NewsContentActivity.actionStart(getActivity(),news.getTitle(),news.getContent());
                    }
                }
            });
            return holder;
        }

        @Override
        //该方法用于对RecyclerView子项的数据进行赋值，会在每个子项被滚动到屏幕内的时候执行
        public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
            News news=mNewsList.get(position);//通过position得到当前项的News实例
            holder.newsTitleText.setText(news.getTitle());//在将数据设置到ViewHolder的newsTitleText
        }

        @Override
        //返回数据源长度
        public int getItemCount() {
            return mNewsList.size();
        }
    }
}