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android多任務同時下載
學習android快兩個月了，一直堅持從迷茫中尋找可以得到的盡可能多的東西
想做一個下載功能，當然理想的功能要支持多任務同時下載，斷點續傳的功能，我想一步一步來，首先困難擺在了多任務這裏
開始我的思路是在一個Service中啟動下載的流操作，然後通過Service中聲明一個Activity中的Handler更新UI(比如進度條。。。)
可是我發現在Service中聲明一個Activity中的Handler是做不到的（可能隻是我做不到吧，無法申請內存）
於是，我決定在Activity中直接啟動線程，讓其運行，調用自身的Handler來更新UI，沒想到在這個下載Activity onPause（）的時候，線程還是活的，也就是說可以繼續下載，下例是我做的一個兩個任務同時下載的小例子，後麵會把理想中的功能都陸續添加上的。。。
package oneRain.MulThreadDownload;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import oneRain.MulThreadDownload.DownloadServicer.DownloadThread;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.widget.ProgressBar;
import android.widget.TextView;
public class MulThreadDownload extends Activity
{
/** Called when the activity is first created. */
private ProgressBar pb1 = null;
private TextView tv1 = null;
private ProgressBar pb2 = null;
private TextView tv2 = null;
private String root = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator;
private String downloadFile = "https://192.168.1.5/android/test.zip";
private String downloadFile1 = "https://192.168.1.5/android/test1.exe";
//聲明已經讀過的長度變量
private int hasRead = 0;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pb1 = (ProgressBar)findViewById(R.id.progressBar1);
tv1 = (TextView)findViewById(R.id.textView1);
pb2 = (ProgressBar)findViewById(R.id.progressBar2);
tv2 = (TextView)findViewById(R.id.textView2);
download(downloadFile, root, pb1, tv1);
download(downloadFile1, root, pb2, tv2);
}
private void download(String url, String targetPath, ProgressBar pb, TextView tv)
{
DownloadThread dt = new DownloadThread(url, targetPath, pb, tv);
dt.start();
}
//自定義一個Handler類，處理線程消息
public class MyHandler extends Handler
{
private ProgressBar progressBar;
private TextView textView;
//通過構造函數來確定給哪個ProgressBar刷新
public MyHandler(ProgressBar progressBar, TextView textView)
{
this.progressBar = progressBar;
this.textView = textView;
}
//萬惡的動詞和名詞
public void handleMessage(Message msg)
{
this.progressBar.setProgress(msg.arg1);
this.textView.setText(msg.arg1 + "%");
super.handleMessage(msg);
}
}
//下載線程
public class DownloadThread extends Thread
{
private String url = "";
private String targetPath = "";
private int hasDownload = 0;
private int len = -1;
private byte buffer[] = new byte[4 * 1024];
private int size = 0;
private int rate = 0;
private MyHandler myHandler = null;
private Message msg = null;
private ProgressBar pb = null;
private TextView tv = null;
public DownloadThread(String url, String targetPath, ProgressBar pb, TextView tv)
{
this.url = url;
this.targetPath = targetPath;
this.pb = pb;
this.tv = tv;
myHandler = new MyHandler(this.pb, this.tv);
}
public void run()
{
String targetFileName = this.targetPath + this.url.substring(this.url.lastIndexOf("/")+1, this.url.length());
File downloadFile = new File(targetFileName);
if(!downloadFile.exists())
{
try
{
downloadFile.createNewFile();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
URL fileUrl = new URL(this.url);
HttpURLConnection conn = (HttpURLConnection)fileUrl.openConnection();
//獲取文件大小
size = conn.getContentLength();
InputStream is = conn.getInputStream();
OutputStream os = new FileOutputStream(targetFileName);
while((len=is.read(buffer)) != -1)
{
os.write(buffer);
hasDownload += len;
rate = (hasDownload*100/size);
msg = new Message();
msg.arg1 = rate;
myHandler.sendMessage(msg);
System.out.println(rate + "%");
}
}
catch (MalformedURLException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
最後更新：2017-04-02 06:51:48