android Service實現後臺下載

功能：點擊按鈕，啓動一個Service下載指定地址的內容，並且將內容保存到Sdcard卡，下載時發送一個進度條通知到通知欄。

Activity 類：

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;

public class MainActivity extends Activity {
    private String PATH = "http://e.hiphotos.baidu.com/image/pic/item/63d9f2d3572c11dfbdb69872612762d0f703c27f.jpg";//數據地址，這裏給了一張圖片地址
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.button1).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent intent = new Intent(MainActivity.this, GetPictures.class);
                intent.putExtra("PATH", PATH);//傳遞一個參數
                startService(intent);//開啓服務
            }
        });
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

Service 繼承類：

import java.io.ByteArrayOutputStream;
import java.io.InputStream;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.widget.Toast;

public class GetPictures extends Service {
    private String PATH = "";
    private Notification.Builder builder;
    private NotificationManager manager;
    private Handler handler = new Handler() {// 消息隊列
        @Override
        public void handleMessage(android.os.Message msg) {
            super.handleMessage(msg);
            if (msg.what == 1) {
                stopSelf();
                Toast.makeText(getApplicationContext(), "下載完成", 1).show();
            }
        }
    };

    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onCreate() {
        // TODO Auto-generated method stub
        super.onCreate();
        manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        builder = new Notification.Builder(getApplicationContext());
        builder.setSmallIcon(R.drawable.ic_launcher).setTicker("下載圖片")
                .setContentTitle("圖片下載").setContentText("正在下載圖片")
                .setAutoCancel(true);// 用戶點擊瀏覽一次後，通知消失;
    }

    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // TODO Auto-generated method stub
        PATH = intent.getStringExtra("PATH");// 接受傳遞過來的參數
        new myTast().start();// 創建一個新的線程並且啓動
        return super.onStartCommand(intent, flags, startId);

    }

    public class myTast extends Thread implements Runnable {
        @Override
        public void run() {
            // TODO Auto-generated method stub
            super.run();
            HttpClient client = new DefaultHttpClient();
            HttpGet get = new HttpGet(PATH);
            HttpResponse httpResponse;
            InputStream inputStream = null;
            ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
            int len = 0;
            int len_data = 0;
            byte[] data = new byte[512];
            try {
                httpResponse = client.execute(get);
                long len_long = httpResponse.getEntity().getContentLength();
                if (httpResponse.getStatusLine().getStatusCode() == 200) {
                    ToSdcard to = new ToSdcard();
                    inputStream = httpResponse.getEntity().getContent();
                    while ((len = inputStream.read(data)) != -1) {
                        arrayOutputStream.write(data, 0, data.length);
                        len_data += len;
                        int progress_value = (int) ((len_data / (float) len_long) * 100);//進度條刻度計算
                        builder.setProgress(100, progress_value, false);
                        manager.notify(1000, builder.build());
                    }
                    boolean flag = to.saver("bb.png",//保存的文件名
                            arrayOutputStream.toByteArray());// 數據保存到本地Sdcard
                    builder.setContentText("下載完成!");
                    manager.notify(1000, builder.build());
                    if (flag) {
                        handler.sendEmptyMessage(1);
                    }
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

佈局文件中只有一個按鈕，就不貼源碼了，記得在清單文件中聲明服務以及獲取連網權限和Sdcard卡讀寫權限

<service android:name=".GetPictures"></service>

 <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

http://blog.csdn.net/q296264785/article/details/53155739