Android之SwipeRefreshLayout下拉刷新

SwipeRefreshLayout是谷歌内部提供的一款下拉刷新,我使用了一下并配合抓取网络Json数据贼好用
因为我抓的是网络数据需要加网络权限

//这是网络权限
 <uses-permission android:name="android.permission.INTERNET"/>

然后是创建一个网络请求的构造器,这个构造器的作用是可以从外界传一个地址进来

package com.example.ryan.swiperefresh;

import android.net.Uri;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class Fetcher {
    private String address;

    public Fetcher(String address){
        this.address=address;
    }

    public String fetcher() {
        String info="";
        try {
            URL url=new URL("https://api.myjson.com/bins/8sd7h");
            HttpURLConnection connection= (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            InputStream inputStream=connection.getInputStream();
            //如果获取到编码格式使用这个代码
//            String encoding=connection.getContentEncoding();
            int len =connection.getContentLength();
            byte[] buf=new byte[len];
            inputStream.read(buf);
            //获取到编码格式传递Encoding
//            info=new String(buf,encoding);
            info=new String(buf);
        } catch (IOException e) {
            e.printStackTrace();
        }

        return info;
    }
}

创建完这个构造器,我重写了一个ListViewAdapter,我个人觉得重写ListView比给的Arrayadapter和SimpleAdapter要简单
重写ListView需要一个类,我这里是一个User类

package com.example.ryan.swiperefresh;

public class User {
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    String name;
    int age;
}

有了类需要一个Adapter,所以建立一个UserAdapter

package com.example.ryan.swiperefresh;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import java.util.List;

public class UserAdapter extends ArrayAdapter<User> {
    private Context context;
    private int resource;
    private List<User> users;
    public UserAdapter(@NonNull Context context, int resource, List<User> users) {
        super(context, resource, users);
        this.context=context;
        this.users=users;
        this.resource=resource;
    }

    @Override
    public int getCount() {
        return users.size();
    }

    @Nullable
    @Override
    public User getItem(int position) {
        return users.get(position);
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null){
            convertView=LayoutInflater.from(this.context).inflate(this.resource,parent,false);
        }
        TextView userTv=convertView.findViewById(R.id.userTv);
        TextView ageTv=convertView.findViewById(R.id.ageTv);

        userTv.setText(users.get(position).getName());
        ageTv.setText(users.get(position).getAge()+"");
        return convertView;
    }
}

这里我们需要一个布局文件,来排列ListView,我这么做了一个user_layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:orientation="horizontal"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/userTv"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/ageTv"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content" />

</LinearLayout>

我这里只是简单渲染一下name和age,并不复杂

我们看一下activity_main的内容

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/swipe_ly"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <ListView
            android:id="@+id/listview"
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </ListView>

    </android.support.v4.widget.SwipeRefreshLayout>

</LinearLayout>

这里没有什么过多的东西,SwipeRefreshLayout的定义和ListView的定义

接下来我们来看一下Json的解析和下拉更新

package com.example.ryan.swiperefresh;

import android.os.Handler;
import android.os.Message;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

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

public class MainActivity extends AppCompatActivity {
    private String address="https://api.myjson.com/bins/8sd7h";
    private ListView listview;
    private SwipeRefreshLayout swipeRefreshLayout;
    private List<User> user;
    private UserAdapter adapter;
    private Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        user=new ArrayList<>();
        adapter=new UserAdapter(this,R.layout.user_layout,user);
        listview=findViewById(R.id.listview);
        listview.setAdapter(adapter);
        swipeRefreshLayout=findViewById(R.id.swipe_ly);

        //在listview上做一个下拉刷新的监听
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                handler=new Handler(){
                    @Override
                    public void handleMessage(Message msg) {
                        if (msg.what==1){
                            adapter.notifyDataSetChanged();
                            swipeRefreshLayout.setRefreshing(false);
                        }
                    }
                };
                new Thread(){
                    @Override
                    public void run() {
                        String info=new Fetcher(address).fetcher();
                        try {
                            JSONArray jsa=new JSONArray(info);
                            for (int i=0;i<jsa.length();i++){
                                JSONObject jso=jsa.getJSONObject(i);
                                User u=new User();
                                u.setName(jso.getString("name"));
                                u.setAge(jso.getInt("age"));
                                user.add(u);
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        handler.sendEmptyMessage(1);

                    }
                }.start();
                //在这做下拉操作
                //我这里放了一个handle模拟延时操作
                //模拟网络请求需要3000毫秒，请求完成，设置setRefreshing 为false
//                new Handler().postDelayed(new Runnable() {
//                    @Override
//                    public void run() {
//                        swipeRefreshLayout.setRefreshing(false);
//                    }
//                }, 3000);

            }
        });
    }

}

这样我们就做出了没下拉一次更新一次

效果大概这样

image.png

image.png

image.png