android多任务下载的状态更新

对于下载任务，通常需要实时的更新任务进度

一般而言，最直接的方式是使用AsyncTask对进度进行实时更新

但对于多个任务并且界面切换后，AsyncTask并不能满足要求

此时需要使用service，进行独立的下载操作，而进度的更新可以通过不断的广播来更新需要展示的进度

代码片段

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1. package com.exam;  
2.   
3. import java.io.File;  
4. import java.io.IOException;  
5. import java.io.InputStream;  
6. import java.io.RandomAccessFile;  
7. import java.net.HttpURLConnection;  
8. import java.net.URL;  
9. import java.util.concurrent.Executors;  
10. import java.util.concurrent.ThreadPoolExecutor;  
11.   
12. import android.app.Service;  
13. import android.content.Intent;  
14. import android.net.Uri;  
15. import android.os.Handler;  
16. import android.os.IBinder;  
17. import android.text.TextUtils;  
18. import android.util.Log;  
19.   
20. import com.exam.utils.FileUtils;  
21.   
22. public class DownloadService extends Service {  
23.   
24.     private boolean stop;  
25.     public static final String ACTION_DOWNLOAD = "com.exam.downloadservice";  
26.     private static ThreadPoolExecutor sExecutorService = (ThreadPoolExecutor) Executors  
27.             .newFixedThreadPool(3);  
28.     private String sAppId;  
29.     private Handler mHandler = new Handler() {  
30.         public void handleMessage(android.os.Message msg) {  
31.             int what = msg.what;  
32.             if (stop) {  
33.                 return;  
34.             }  
35.             if (what == 0) {  
36.                 if (msg.obj != null && msg.obj instanceof Intent) {  
37.                     Intent intent = (Intent) msg.obj;  
38.                     DownloadService.this.sendBroadcast(intent);  
39.                 }  
40.             } else if (what == 2) {  
41.                 try {  
42.                     Intent instIntent = new Intent(Intent.ACTION_VIEW);  
43.                     instIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  
44.                     instIntent.setDataAndType(  
45.                             Uri.fromFile(new File(msg.obj.toString())),  
46.                             "application/vnd.android.package-archive");  
47.                     startActivity(instIntent);  
48.                 } catch (Exception e) {  
49.                     e.printStackTrace();  
50.                 }  
51.             }  
52.         }  
53.     };  
54.   
55.     private class DownloadTask implements Runnable {  
56.         private String mLocalPath = FileUtils.SDCARD_BACKUP_APP;  
57.         private String mAppId;  
58.         private String mDownloadUrl;  
59.         private String mLocalName = "tmp.apk";  
60.         private String mFileSize;  
61.         /** 
62.          * -2等待-1失败,0执行前, 1执行中 ,2成功 
63.          */  
64.         // private int flag = -2;   
65.   
66.         private long mTotalSize;  
67.         private long mDownloadedSize;  
68.         private long mDownloadedSpeed;  
69.         private int mProgress;  
70.   
71.         public DownloadTask(String appId, String appName, String downloadUrl,  
72.                 long size) {  
73.             this.mAppId = appId;  
74.             this.mLocalName = appName + ".apk";  
75.             this.mDownloadUrl = downloadUrl;  
76.             this.mFileSize = FileUtils.getFormatSize(size);  
77.         }  
78.   
79.         protected void onPreExecute(int flag) {  
80.             mTotalSize = 0;  
81.             mDownloadedSize = 0;  
82.             mDownloadedSpeed = 1;  
83.             mProgress = 0;  
84.             publishProgress(flag);  
85.         }  
86.   
87.         protected void onPostExecute(int flag) {  
88.             publishProgress(flag);  
89.         }  
90.   
91.         private void publishProgress(int flag) {  
92.             if (mProgress > 100) {  
93.                 mProgress = 100;  
94.             }  
95.             if (mProgress < 0) {  
96.                 mProgress = 0;  
97.             }  
98.   
99.             StringBuffer bufferState = new StringBuffer();  
100.             bufferState.append(FileUtils.getFormatSize(mDownloadedSize))  
101.                     .append("/").append(mFileSize);  
102.   
103.             StringBuffer bufferSpeed = new StringBuffer();  
104.             bufferSpeed.append(FileUtils.getFormatSize(mDownloadedSpeed))  
105.                     .append("/s");  
106.   
107.             Intent intent = new Intent(ACTION_DOWNLOAD);  
108.             intent.putExtra("appId", mAppId);  
109.             intent.putExtra("state", bufferState.toString());  
110.             intent.putExtra("speed", bufferSpeed.toString());  
111.             intent.putExtra("progress", this.mProgress);  
112.             // -2等待-1失败,0执行前, 1执行中 ,2成功   
113.             intent.putExtra("flag", flag);  
114.             mHandler.sendMessage(mHandler.obtainMessage(0, intent));  
115.             if (flag == 2) {  
116.                 String path = FileUtils.SDCARD_BACKUP_APP + mLocalName;  
117.                 mHandler.sendMessage(mHandler.obtainMessage(2, path));  
118.             }  
119.         }  
120.   
121.         public void execute() {  
122.             int flag = 0;  
123.             onPreExecute(flag);  
124.             flag = 1;  
125.             boolean result = downloadFile(flag);  
126.             if (result) {  
127.                 flag = 2;  
128.             } else {  
129.                 flag = -1;  
130.             }  
131.             onPostExecute(flag);  
132.         }  
133.   
134.         private boolean downloadFile(int flag) {  
135.             InputStream inputStream = null;  
136.             RandomAccessFile raf = null;  
137.             try {  
138.                 // 检查文件夹是否存在，如果不存在就创建   
139.                 File dir = new File(mLocalPath);  
140.                 if (!dir.exists()) {  
141.                     dir.mkdirs();  
142.                 }  
143.   
144.                 File file = new File(mLocalPath, mLocalName);  
145.                 if (file.exists()) {  
146.                     // downloadedSize = file.length();   
147.                     // raf.seek(downloadedSize);   
148.                     file.delete();  
149.                 }  
150.                 raf = new RandomAccessFile(file, "rw");  
151.   
152.                 URL url = new URL(mDownloadUrl);  
153.                 HttpURLConnection urlConnection = (HttpURLConnection) url  
154.                         .openConnection();  
155.                 urlConnection.setRequestMethod("GET");  
156.                 // urlConnection   
157.                 // .setRequestProperty("RANGE", "bytes=" + downloadedSize);   
158.                 urlConnection.setDoOutput(true);  
159.                 urlConnection.connect();  
160.                 inputStream = urlConnection.getInputStream();  
161.                 mTotalSize = urlConnection.getContentLength();  
162.                 byte[] buffer = new byte[1024];  
163.                 int bufferLength = 0;  
164.   
165.                 // kb   
166.                 long beginTime = System.currentTimeMillis();  
167.                 long endTime = beginTime;  
168.                 long size = 0;  
169.                 while ((bufferLength = inputStream.read(buffer)) > 0) {  
170.                     if (mAppId.equals(sAppId) || stop) {  
171.                         inputStream.close();  
172.                         inputStream = null;  
173.                         sAppId = null;  
174.                         return false;  
175.                     }  
176.                     raf.write(buffer, 0, bufferLength);  
177.                     mDownloadedSize += bufferLength;  
178.   
179.                     size += bufferLength;  
180.                     endTime = System.currentTimeMillis();  
181.                     if (endTime - beginTime >= 1000) {  
182.                         // kb   
183.                         mDownloadedSpeed = size;  
184.                         mProgress = (int) (100 * mDownloadedSize / mTotalSize);  
185.                         publishProgress(flag);  
186.   
187.                         beginTime = endTime;  
188.                         size = 0;  
189.                     }  
190.   
191.                 }  
192.                 raf.close();  
193.                 raf = null;  
194.                 inputStream.close();  
195.                 inputStream = null;  
196.             } catch (Exception e) {  
197.                 e.printStackTrace();  
198.                 return false;  
199.             } finally {  
200.                 try {  
201.                     if (raf != null) {  
202.                         raf.close();  
203.                         raf = null;  
204.                     }  
205.                     if (inputStream != null) {  
206.                         inputStream.close();  
207.                         inputStream = null;  
208.                     }  
209.                 } catch (IOException e) {  
210.                     e.printStackTrace();  
211.                 }  
212.             }  
213.   
214.             return true;  
215.         }  
216.   
217.         @Override  
218.         public void run() {  
219.             execute();  
220.         }  
221.     }  
222.   
223.     private void execute(Runnable runnable) {  
224.         sExecutorService.execute(runnable);  
225.     }  
226.   
227.     @Override  
228.     public void onCreate() {  
229.         super.onCreate();  
230.         stop = false;  
231.   
232.     }  
233.   
234.     @Override  
235.     public void onDestroy() {  
236.         super.onDestroy();  
237.         stop = true;  
238.         mHandler.removeMessages(0);  
239.         new Thread() {  
240.             @Override  
241.             public void run() {  
242.                 FileUtils.deleteFiles(new File(FileUtils.SDCARD_BACKUP_APP));  
243.             }  
244.         }.start();  
245.     }  
246.   
247.     @Override  
248.     public int onStartCommand(Intent intent, int flags, int startId) {  
249.         Log.v("DownloadService", "onStartCommand.intent=" + intent);  
250.         if (intent != null) {  
251.             String appId = intent.getStringExtra("appId");  
252.             String appName = intent.getStringExtra("appName");  
253.             String downloadUrl = intent.getStringExtra("downloadUrl");  
254.             long fileSize = intent.getLongExtra("fileSize", 0);  
255.             boolean stop = intent.getBooleanExtra("stop", false);  
256.             if (!TextUtils.isEmpty(appId)) {  
257.                 if (stop) {  
258.                     sAppId = appId;  
259.                 } else {  
260.                     if (sExecutorService.getActiveCount() == 3) {  
261.                         // 超出最大线程池数，提示稍后下载   
262.                         Intent intent2 = new Intent(ACTION_DOWNLOAD);  
263.                         intent2.putExtra("appId", appId);  
264.                         intent2.putExtra("state", "");  
265.                         intent2.putExtra("speed", "");  
266.                         intent2.putExtra("progress", 0);  
267.                         // -2等待-1失败,0执行前, 1执行中 ,2成功   
268.                         intent2.putExtra("flag", -2);  
269.                         mHandler.sendMessage(mHandler.obtainMessage(0, intent2));  
270.                     } else {  
271.                         DownloadTask task = new DownloadTask(appId, appName,  
272.                                 downloadUrl, fileSize);  
273.                         execute(task);  
274.                     }  
275.                 }  
276.             }  
277.         }  
278.         return super.onStartCommand(intent, flags, startId);  
279.     }  
280.   
281.     @Override  
282.     public IBinder onBind(Intent intent) {  
283.         return null;  
284.     }  
285. }  

package com.exam;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

import android.app.Service;
import android.content.Intent;
import android.net.Uri;
import android.os.Handler;
import android.os.IBinder;
import android.text.TextUtils;
import android.util.Log;

import com.exam.utils.FileUtils;

public class DownloadService extends Service {

	private boolean stop;
	public static final String ACTION_DOWNLOAD = "com.exam.downloadservice";
	private static ThreadPoolExecutor sExecutorService = (ThreadPoolExecutor) Executors
			.newFixedThreadPool(3);
	private String sAppId;
	private Handler mHandler = new Handler() {
		public void handleMessage(android.os.Message msg) {
			int what = msg.what;
			if (stop) {
				return;
			}
			if (what == 0) {
				if (msg.obj != null && msg.obj instanceof Intent) {
					Intent intent = (Intent) msg.obj;
					DownloadService.this.sendBroadcast(intent);
				}
			} else if (what == 2) {
				try {
					Intent instIntent = new Intent(Intent.ACTION_VIEW);
					instIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
					instIntent.setDataAndType(
							Uri.fromFile(new File(msg.obj.toString())),
							"application/vnd.android.package-archive");
					startActivity(instIntent);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	};

	private class DownloadTask implements Runnable {
		private String mLocalPath = FileUtils.SDCARD_BACKUP_APP;
		private String mAppId;
		private String mDownloadUrl;
		private String mLocalName = "tmp.apk";
		private String mFileSize;
		/**
		 * -2等待-1失败,0执行前, 1执行中 ,2成功
		 */
		// private int flag = -2;

		private long mTotalSize;
		private long mDownloadedSize;
		private long mDownloadedSpeed;
		private int mProgress;

		public DownloadTask(String appId, String appName, String downloadUrl,
				long size) {
			this.mAppId = appId;
			this.mLocalName = appName + ".apk";
			this.mDownloadUrl = downloadUrl;
			this.mFileSize = FileUtils.getFormatSize(size);
		}

		protected void onPreExecute(int flag) {
			mTotalSize = 0;
			mDownloadedSize = 0;
			mDownloadedSpeed = 1;
			mProgress = 0;
			publishProgress(flag);
		}

		protected void onPostExecute(int flag) {
			publishProgress(flag);
		}

		private void publishProgress(int flag) {
			if (mProgress > 100) {
				mProgress = 100;
			}
			if (mProgress < 0) {
				mProgress = 0;
			}

			StringBuffer bufferState = new StringBuffer();
			bufferState.append(FileUtils.getFormatSize(mDownloadedSize))
					.append("/").append(mFileSize);

			StringBuffer bufferSpeed = new StringBuffer();
			bufferSpeed.append(FileUtils.getFormatSize(mDownloadedSpeed))
					.append("/s");

			Intent intent = new Intent(ACTION_DOWNLOAD);
			intent.putExtra("appId", mAppId);
			intent.putExtra("state", bufferState.toString());
			intent.putExtra("speed", bufferSpeed.toString());
			intent.putExtra("progress", this.mProgress);
			// -2等待-1失败,0执行前, 1执行中 ,2成功
			intent.putExtra("flag", flag);
			mHandler.sendMessage(mHandler.obtainMessage(0, intent));
			if (flag == 2) {
				String path = FileUtils.SDCARD_BACKUP_APP + mLocalName;
				mHandler.sendMessage(mHandler.obtainMessage(2, path));
			}
		}

		public void execute() {
			int flag = 0;
			onPreExecute(flag);
			flag = 1;
			boolean result = downloadFile(flag);
			if (result) {
				flag = 2;
			} else {
				flag = -1;
			}
			onPostExecute(flag);
		}

		private boolean downloadFile(int flag) {
			InputStream inputStream = null;
			RandomAccessFile raf = null;
			try {
				// 检查文件夹是否存在，如果不存在就创建
				File dir = new File(mLocalPath);
				if (!dir.exists()) {
					dir.mkdirs();
				}

				File file = new File(mLocalPath, mLocalName);
				if (file.exists()) {
					// downloadedSize = file.length();
					// raf.seek(downloadedSize);
					file.delete();
				}
				raf = new RandomAccessFile(file, "rw");

				URL url = new URL(mDownloadUrl);
				HttpURLConnection urlConnection = (HttpURLConnection) url
						.openConnection();
				urlConnection.setRequestMethod("GET");
				// urlConnection
				// .setRequestProperty("RANGE", "bytes=" + downloadedSize);
				urlConnection.setDoOutput(true);
				urlConnection.connect();
				inputStream = urlConnection.getInputStream();
				mTotalSize = urlConnection.getContentLength();
				byte[] buffer = new byte[1024];
				int bufferLength = 0;

				// kb
				long beginTime = System.currentTimeMillis();
				long endTime = beginTime;
				long size = 0;
				while ((bufferLength = inputStream.read(buffer)) > 0) {
					if (mAppId.equals(sAppId) || stop) {
						inputStream.close();
						inputStream = null;
						sAppId = null;
						return false;
					}
					raf.write(buffer, 0, bufferLength);
					mDownloadedSize += bufferLength;

					size += bufferLength;
					endTime = System.currentTimeMillis();
					if (endTime - beginTime >= 1000) {
						// kb
						mDownloadedSpeed = size;
						mProgress = (int) (100 * mDownloadedSize / mTotalSize);
						publishProgress(flag);

						beginTime = endTime;
						size = 0;
					}

				}
				raf.close();
				raf = null;
				inputStream.close();
				inputStream = null;
			} catch (Exception e) {
				e.printStackTrace();
				return false;
			} finally {
				try {
					if (raf != null) {
						raf.close();
						raf = null;
					}
					if (inputStream != null) {
						inputStream.close();
						inputStream = null;
					}
				} catch (IOException e) {
					e.printStackTrace();
				}
			}

			return true;
		}

		@Override
		public void run() {
			execute();
		}
	}

	private void execute(Runnable runnable) {
		sExecutorService.execute(runnable);
	}

	@Override
	public void onCreate() {
		super.onCreate();
		stop = false;

	}

	@Override
	public void onDestroy() {
		super.onDestroy();
		stop = true;
		mHandler.removeMessages(0);
		new Thread() {
			@Override
			public void run() {
				FileUtils.deleteFiles(new File(FileUtils.SDCARD_BACKUP_APP));
			}
		}.start();
	}

	@Override
	public int onStartCommand(Intent intent, int flags, int startId) {
		Log.v("DownloadService", "onStartCommand.intent=" + intent);
		if (intent != null) {
			String appId = intent.getStringExtra("appId");
			String appName = intent.getStringExtra("appName");
			String downloadUrl = intent.getStringExtra("downloadUrl");
			long fileSize = intent.getLongExtra("fileSize", 0);
			boolean stop = intent.getBooleanExtra("stop", false);
			if (!TextUtils.isEmpty(appId)) {
				if (stop) {
					sAppId = appId;
				} else {
					if (sExecutorService.getActiveCount() == 3) {
						// 超出最大线程池数，提示稍后下载
						Intent intent2 = new Intent(ACTION_DOWNLOAD);
						intent2.putExtra("appId", appId);
						intent2.putExtra("state", "");
						intent2.putExtra("speed", "");
						intent2.putExtra("progress", 0);
						// -2等待-1失败,0执行前, 1执行中 ,2成功
						intent2.putExtra("flag", -2);
						mHandler.sendMessage(mHandler.obtainMessage(0, intent2));
					} else {
						DownloadTask task = new DownloadTask(appId, appName,
								downloadUrl, fileSize);
						execute(task);
					}
				}
			}
		}
		return super.onStartCommand(intent, flags, startId);
	}

	@Override
	public IBinder onBind(Intent intent) {
		return null;
	}
}

转载地址：http://blog.youkuaiyun.com/hknock/article/details/22884325