androi 多线程

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="当前网络：" />

    <TextView
        android:id="@+id/txt_show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="278dp"
        android:layout_height="wrap_content"
        android:layout_weight="1.14"
         />

</LinearLayout>

java

package app.android.demo;

import android.os.AsyncTask;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;

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

import android.app.Activity;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity
{
    private ImageView mImageView = null ;
    Button mButton1;
    Button mButton2;
    Button mButton3;
    Button mButton4;
    TextView mTextView;
    TextView mTextView1;
    ConnectivityManager connectMgr;
    NetworkInfo[] networkInfo;
    //The image url we are downloading from internet .
    private final String IMAGE_URL1 = "http://a.hiphotos.baidu.com/image/pic/item/c2fdfc039245d688acbcd54ba0c27d1ed31b24a6.jpg" ;
    private final String IMAGE_URL2 = "http://imgsrc.baidu.com/forum/w%3D580/sign=f9f1029647166d223877159c76230945/b69ad3f9d72a6059892764472c34349b023bbaca.jpg" ;
    private final String IMAGE_URL3 = "http://static.open-open.com/lib/uploadImg/20130810/20130810175659_519.jpg" ;
    private final String IMAGE_URL4 = "http://imgsrc.baidu.com/forum/w%3D580/sign=f9f1029647166d223877159c76230945/b69ad3f9d72a6059892764472c34349b023bbaca.jpg" ;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mImageView = (ImageView)this.findViewById(R.id.imageView1) ;
        mButton1=(Button) findViewById(R.id.button1);
        mButton2=(Button) findViewById(R.id.button2);

        mTextView=(TextView) findViewById(R.id.txt_show);
        mTextView1=(TextView) findViewById(R.id.textView1);

        if (isNetworkAvailable(MainActivity.this))
        {

            mButton1.setOnClickListener(new Button1Lislen());
            mButton2.setOnClickListener(new Button2Lislen());
            mTextView1.setText("当前网络:=>可用");
            Toast.makeText(getApplicationContext(), "当前有可用网络！", Toast.LENGTH_LONG).show();
        }
        else
        {
            mTextView1.setText("当前网络:=>不可用");
            Toast.makeText(getApplicationContext(), "当前没有可用网络！", Toast.LENGTH_LONG).show();
        }

    }
   class Button1Lislen implements OnClickListener
   {
    @Override
     public void onClick(View v)
    {
        new Thread(new Runnable(){
            @Override
            public void run() {
                // TODO Auto-generated method stub
                final Drawable drawable = loadImageFromNetwork(IMAGE_URL1);

                mImageView.post(new Runnable(){
                    @Override
                    public void run() {
                        // TODO Auto-generated method stub

                            mImageView.setImageDrawable(drawable) ;

                    }}) ;
            }

        }).start()  ; 

    }
   }

    private Drawable loadImageFromNetwork(String imageUrl)
    {
        Drawable drawable = null;
        try {
            drawable = Drawable.createFromStream(
                    new URL(imageUrl).openStream(), "image.gif");
        } catch (IOException e) {
            Log.d("test", e.getMessage());
        }
        if (drawable == null) {
            Log.d("test", "null drawable");
        } else {
            Log.d("test", "not null drawable");
        }

        return drawable ;
    }

    class Button2Lislen implements OnClickListener
    {
     @Override
     public void onClick(View v)
     {
             new DownloadImageTask().execute(IMAGE_URL2) ;

     }

    }

    private class DownloadImageTask extends AsyncTask<String, Void, Drawable>
    {
        /** The system calls this to perform work in a worker thread and
          * delivers it the parameters given to AsyncTask.execute() */
        protected Drawable doInBackground(String... urls) {
            return loadImageFromNetwork(urls[0]);
        }

        /** The system calls this to perform work in the UI thread and delivers
          * the result from doInBackground() */
        protected void onPostExecute(Drawable result) {
            mImageView.setImageDrawable(result);
        }
    }

    //to see if these is a  network
    public boolean isNetworkAvailable(Activity activity)
    {
        Context context = activity.getApplicationContext();
        // 获取手机所有连接管理对象（包括对wi-fi,net等连接的管理）
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        if (connectivityManager == null)
        {
            return false;
        }
        else
        {
            // 获取NetworkInfo对象
            NetworkInfo[] networkInfo = connectivityManager.getAllNetworkInfo();

            if (networkInfo != null && networkInfo.length > 0)
            {
                for (int i = 0; i < networkInfo.length; i++)
                {
                    System.out.println(i + "===状态===" + networkInfo[i].getState());
                    System.out.println(i + "===类型===" + networkInfo[i].getTypeName());
                    mTextView.setText("===网络状态===>" + networkInfo[i].getState()+"\n"+
                            "===网络类型===>" + networkInfo[i].getTypeName());
                   //Toast.makeText(MainActivity.this, "===状态===" + networkInfo[i].getState()+networkInfo[i].getTypeName(), 3000).show();
                    // 判断当前网络状态是否为连接状态
                    if (networkInfo[i].getState() == NetworkInfo.State.CONNECTED)
                    {
//                        mTextView.setText("===网络状态===>" + networkInfo[i].getState()+"\n"+
//                                "===网络类型===>" + networkInfo[i].getTypeName());
                        return true;
                    }
//                    mTextView.setText("===状态===>" + networkInfo[i].getState()+"\n"+
//                                       "===类型===>" + networkInfo[i].getTypeName());
                }
            }
        }
        return false;
    }  

}

权限：

manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="app.android.demo"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />
    <uses-permission android:name="android.permission.INTERNET"/>
　　<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="app.android.demo.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

效果 :