网络多线程

AndroidManifest.xml

activity_main.xml

MainActivity.java

package com.example.nethanderdemo;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public Handler mHander = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(msg.what == 0x111){
                TextView textView = findViewById(R.id.tv1);
                textView.setText((String) msg.obj);
            }
        }
    };
    public void btnClick1(View view) {
        // 使用网络API 访问百度，将返回的源代码输出到TextView中
        // 一些常见问题
        // 0. 网络操作需要网络权限
        // 1. android中的网络操作属于耗时操作，耗时操作不允许在主线程执行
        // 2. 界面操作只能在主线程操作
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                String path = "http://www.baidu.com";
                try {
                    // 1. 创建URL对象，连接对象，设置信息
                    URL url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setConnectTimeout(5000);
                    // 2. 发出请求，获取响应结果
                    int code = connection.getResponseCode();
                    if(code == 200){
                        // 读取数据，保存数据
                        InputStream inputStream = connection.getInputStream();
                        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
                        byte bytes[] = new byte[1024];
                        int retCount = -1;
                        while(true){
                            retCount = inputStream.read(bytes,0,1024);
                            if(retCount == -1) break;
                            outputStream.write(bytes,0,retCount);
                        }
                        String string = new String(outputStream.toString());
                        Log.d("15pb",string);
//                        TextView textView = findViewById(R.id.tv1);
//                        textView.setText(string);
                        // 1. 创建消息对象
                        Message message = new Message();
                        message.obj = string;
                        message.what = 0x111;
                        // 2. 使用handler发送消息到主线程中
                        mHander.sendMessage(message);
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        Thread thread1 = new Thread(runnable);
        thread1.start();
    }
    public void btnClick0(View view) {
        // 使用Thread，创建对象指定回调，启动线程
        Thread thread = new Thread(){
            @Override
            public void run() {
                super.run();
                Log.d("15pb","thread");
            }
        };
        thread.start();
        //使用Runnable创建回调对象，使用Thread启动
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                Log.d("15pb","runnable");
            }
        };
        Thread thread1 = new Thread(runnable);
        thread1.start();
    }
}