第一阶段：冲刺6（热搜界面完成）Android通过异步加载获取数据

昨天把花了很多时间把热搜界面设计出来了，今天也终于把热搜界面完成了。思想是用了异步加载数据，和java的ajax类似。获取数据就是通过一个网络请求来获得数据库的内容。具体实现效果看下图

上面三个图是用的异步加载获取的数据（进入首页即可获得数据，不用点击），三个按键是之前的测试数据。参考微博热搜和QQ热搜界面，设计成这样的，不好看。数据是从数据库里读取的4.17日阅读量最多的前50篇文章。具体了解界面看上一篇博客。

因为要通过网络获取数据，所以得需要添加访问网络的依赖

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

在res新建一个xml文件夹，新建一个network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>

在AndroidManifest.xml的appliacationn里添加以下语句

android:usesCleartextTraffic="true"
android:networkSecurityConfig="@xml/network_security_config">

这样网络请求就不会报错了。（我的网络请求出了好多错，把这两个加上就没问题了）

具体思路：通过异步请假，发送网络请求，请求数据库数据，返回json格式。因为查询的是多条，所以最后会返回的是json的数组，需要通过gson.fromJson()方法，转换成我们list数组。

代码在昨天的基础上加了很多东西，当然也有一些测试的（删除全部信息，插入等）。

New_实体类

  
package com.example.hotsearch;
import androidx.room.ColumnInfo;

import androidx.room.Entity;

import androidx.room.PrimaryKey;
@Entity

public class New_ {

@PrimaryKey(autoGenerate = true)

private int id;

//    @ColumnInfo(name = "评论数量")

private int commentCount;

//    @ColumnInfo(name = "阅读量")

private int priority;

//    @ColumnInfo(name = "来源")

private String source;

//    @ColumnInfo(name = "标题")

private String title;

//    @ColumnInfo(name = "摘要")

private String digest;

//    @ColumnInfo(name = "图片地址")

private String imgsrc;

//    @ColumnInfo(name = "时间")

private String ptime;

//    @ColumnInfo(name = "正文")

private String zw;

//    @ColumnInfo(name = "类型")

private String type;

private Boolean history = false;
public New_(int priority, String title) {
    this.priority = priority;
    this.title = title;
}

public Boolean getHistory() {
    return history;
}

public void setHistory(Boolean history) {
    this.history = history;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public int getCommentCount() {
    return commentCount;
}

public void setCommentCount(int commentCount) {
    this.commentCount = commentCount;
}

public int getPriority() {
    return priority;
}

public void setPriority(int priority) {
    this.priority = priority;
}

public String getSource() {
    return source;
}

public void setSource(String source) {
    this.source = source;
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getDigest() {
    return digest;
}

public void setDigest(String digest) {
    this.digest = digest;
}

public String getImgsrc() {
    return imgsrc;
}

public void setImgsrc(String imgsrc) {
    this.imgsrc = imgsrc;
}

public String getPtime() {
    return ptime;
}

public void setPtime(String ptime) {
    this.ptime = ptime;
}

public String getZw() {
    return zw;
}

public void setZw(String zw) {
    this.zw = zw;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

}

Adapter适配器

  
package com.example.hotsearch;
import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.EditText;

import android.widget.TextView;

import androidx.annotation.NonNull;

import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;

import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

List<New_> allNews = new ArrayList<>();
public void setAllNews(List<New_> allNews) {
    this.allNews = allNews;
}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
    View itemViem = layoutInflater.inflate(R.layout.cell_normal, parent,false);
    return new MyViewHolder(itemViem);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
    New_ new_ = allNews.get(position);
    holder.textViewNumber.setText(String.valueOf(position+1));
    holder.editTextTitle.setText(new_.getTitle());
    holder.editTextTitle.setEnabled(false);
    holder.editTextTitle.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });
    holder.textViewSearchNum.setText(new_.getPriority()+"人查询");
}

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

//用来管理我们新建的ConstraintLayout
static class MyViewHolder extends RecyclerView.ViewHolder {
    TextView textViewNumber,textViewSearchNum;
    EditText editTextTitle;
    public MyViewHolder(@NonNull View itemView) {
        super(itemView);
        textViewNumber = itemView.findViewById(R.id.textViewNumber);
        editTextTitle = itemView.findViewById(R.id.editTextTitle);
        textViewSearchNum = itemView.findViewById(R.id.textViewSearchNum);
    }
}

}

NewsDao

  
package com.example.hotsearch;
import androidx.lifecycle.LiveData;

import androidx.room.Dao;

import androidx.room.Insert;

import androidx.room.Query;
import java.util.List;
@Dao

public interface NewsDao {

@Insert

public void insertNews(New_...new_s);

@Query("SElECT * FROM New_")

public LiveData<List<New_>> getAllNewsLive();

@Query("DELETE FROM New_")

public void deleteAllNews();

}

************读取的可不是这个数据库，这个数据库是存放我们的新闻，和我们读取的没关系。真正读取的是我们自己的mysql数据库

NewsDatabase(数据库)

  
package com.example.hotsearch;
import android.content.Context;
import androidx.room.Database;

import androidx.room.Room;

import androidx.room.RoomDatabase;

@Database(entities = {New_.class},version = 1,exportSchema = false)

public abstract class NewsDatabase extends RoomDatabase {

private static NewsDatabase INSTANCE;

static synchronized NewsDatabase getDatabase(Context context){

if(INSTANCE == null){

INSTANCE = Room.databaseBuilder(context.getApplicationContext(),NewsDatabase.class,"new_database")

.allowMainThreadQueries()

.build();

}

return INSTANCE;

}

public abstract NewsDao getNewsDao();

工程类添加了网络请假方法和内部类来实现我们的异步请求

NewsRepository

  
package com.example.hotsearch;
import android.content.Context;

import android.os.AsyncTask;

import android.util.Log;
import androidx.lifecycle.LiveData;
import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;
import java.io.ByteArrayOutputStream;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.List;
public class NewsRepository {

private LiveData<List<New_>> allNews;

private NewsDao newsDao;

public NewsRepository(Context context) {

NewsDatabase wordDatabase = NewsDatabase.getDatabase(context.getApplicationContext());

newsDao = wordDatabase.getNewsDao();

allNews = newsDao.getAllNewsLive();

}
public LiveData<List<New_>> getAllNews() {
    return allNews;
}
// 定义类的接口-- 插入
public void insertNews(New_...news){
    new InsertAsyncTask(newsDao).execute(news);
}
public void deleteNews(){
    new DeleteAsyncTask(newsDao).execute();
}
// 插入类
static class InsertAsyncTask extends AsyncTask<New_,Void,Void> {
    private NewsDao newsDao;
    public InsertAsyncTask(NewsDao newsDao) {
        this.newsDao = newsDao;
    }
    // 将在主线程的工作放到后台来执行
    @Override
    protected Void doInBackground(New_...new_s) {
       newsDao.insertNews(new_s);
        return null;
    }
}
// 删除类
static class DeleteAsyncTask extends AsyncTask<New_,Void,Void> {
    private NewsDao newsDao;
    public DeleteAsyncTask(NewsDao newsDao) {
        this.newsDao = newsDao;
    }
    // 将在主线程的工作放到后台来执行
    @Override
    protected Void doInBackground(New_...new_s) {
        newsDao.deleteAllNews();
        return null;
    }
}
// 创建一个内部类来实现 ,在实现下面内部类之前,需要自定义的Bean对象来封装处理Josn格式的数据
class  NewsAsyncTask extends AsyncTask<String,Void,List<New_>>{
    @Override
    protected List<New_> doInBackground(String... strings) {
         getJson(strings[0]);
        return null;
    }
}
public void getJson(final String address) {
    new Thread(new Runnable(){
        @Override
        public void run() {
            HttpURLConnection connection = null;
            try {
                URL url = new URL(address);
                Log.d("address",address);
                connection=(HttpURLConnection) url.openConnection();
                connection.setRequestMethod("POST");
                connection.setConnectTimeout(10000);
                connection.setReadTimeout(5000);
                connection.connect();
                int code=connection.getResponseCode();
                if(code==200){
                    InputStream is=connection.getInputStream();
                    String state = getStringFromInputStream(is);
                    Gson gson = new Gson();
                    List<New_> list = gson.fromJson(state,new TypeToken<List<New_>>(){}.getType());
                    for (int i=0;i<50;i++){
                        New_ new_2 = new New_(list.get(i).getPriority(),list.get(i).getTitle());
                        newsDao.insertNews(new_2);
                    }
                }

            } catch (Exception e) {
                e.printStackTrace();
            }finally{
                if(connection!=null){
                    connection.disconnect();
                }
            }
        }
    }).start();

}
private static String getStringFromInputStream(InputStream is) throws Exception{

    ByteArrayOutputStream baos=new ByteArrayOutputStream();
    byte[] buff=new byte[1024];
    int len=-1;
    while((len=is.read(buff))!=-1){
        baos.write(buff, 0, len);
    }
    is.close();
    String html=baos.toString();
    baos.close();
    return html;
}

}

NewsViewModel

  
package com.example.hotsearch;
import android.app.Application;
import androidx.annotation.NonNull;

import androidx.lifecycle.AndroidViewModel;

import androidx.lifecycle.LiveData;
import java.util.List;
public class NewsViewModel extends AndroidViewModel {

private NewsRepository newsRepository;

public NewsViewModel(@NonNull Application application) {

super(application);

newsRepository = new NewsRepository(application);

}
public LiveData<List<New_>> getAllNews() {
    return newsRepository.getAllNews();
}

// 定义类的接口-- 插入
public void insertWords(New_...news){
   newsRepository.insertNews(news);
}
public void deleteWords(New_...news){
   newsRepository.deleteNews();
}
public void getJson(String url){
   newsRepository.getJson(url);
}

}

MainActivity

  
package com.example.hotsearch;
import androidx.appcompat.app.AppCompatActivity;

import androidx.lifecycle.Observer;

import androidx.lifecycle.ViewModelProviders;

import androidx.recyclerview.widget.LinearLayoutManager;

import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;
import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;
import java.io.ByteArrayOutputStream;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.List;
public class MainActivity extends AppCompatActivity {

Button buttonInsert,buttonClear,buttonNews;

NewsViewModel newsViewModel;

RecyclerView recyclerView;

MyAdapter myAdapter;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);
    final String[] url = {"你要访问的网络请求地址"};
    buttonInsert = findViewById(R.id.buttonInsert);
    buttonNews = findViewById(R.id.buttonNews);
    buttonClear = findViewById(R.id.button);
    recyclerView = findViewById(R.id.RecyclerView);
    myAdapter = new MyAdapter();
    newsViewModel = ViewModelProviders.of(this).get(NewsViewModel.class);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.setAdapter(myAdapter);
    newsViewModel.getJson(url[0]);
    newsViewModel.getAllNews().observe(this, new Observer<List<New_>>() {
        @Override
        public void onChanged(List<New_> new_s) {
            myAdapter.setAllNews(new_s);
            myAdapter.notifyDataSetChanged();
        }
    });
    buttonInsert.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            New_ new_2 = new New_(400,"aaa");
            newsViewModel.insertWords(new_2);
        }
    });
    buttonClear.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            newsViewModel.deleteWords();
        }
    });

//        buttonNews.setOnClickListener(new View.OnClickListener() {

//            @Override

//            public void onClick(View v) {

//

//            }

//        });
}

}