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
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