android之网络操作(1)

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

        <Button
           android:id="@+id/btn"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="@string/delete"
           />
        <ImageView
            android:id="@+id/img"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:src="@drawable/dog1"
            />
</LinearLayout>

package xidian.dy.com.chujia;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity {
    private static ImageView img;
    static  MainActivity ma;
    static Handler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = (Button) findViewById(R.id.btn);
        ma = this;
        handler = new Handler(){
            @Override
            //此方法在主线程中刷新UI
            public void handleMessage(Message msg) {
                if(img != null){
                    if(msg.what == 0)
                        img.setImageBitmap((Bitmap)msg.obj);
                    else
                        Toast.makeText(ma,"图片下载失败",Toast.LENGTH_SHORT).show();
                }
            }
        };
        if(btn != null)
            btn.setOnClickListener(new MyLister());
    }

    class MyLister implements View.OnClickListener{
        @Override
        public void onClick(View v) {
            img = (ImageView) findViewById(R.id.img);
            new Thread(){
                @Override
                public void run() {
                    try {
                        URL url = new URL("http://192.168.0.119/dog.jpg");
                        //创建连接对象
                        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                        //设置请求方式
                        conn.setRequestMethod("GET");
                        //设置TCP连接超时
                        conn.setConnectTimeout(5000);
                        //设置http响应超时
                        conn.setReadTimeout(5000);
                        //建立连接
                        conn.connect();
                        Message msg = handler.obtainMessage();
                        if(conn.getResponseCode() == 200){
                            InputStream is = conn.getInputStream();
                            Bitmap bm = BitmapFactory.decodeStream(is);
                            msg.what = 0;
                            msg.obj = bm;
                            handler.sendMessage(msg);
                        }
                        else {
                            msg.what = 1;
                            handler.sendMessage(msg);
                        }
                        Toast.makeText(MainActivity.this, "下载失败", Toast.LENGTH_SHORT).show();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }.start();
        }
    }
}