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android 之斷點續傳詳解三部曲之[一] → 多任務下載
項目需求,需要做一個下載功能，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。。。。。。
首先是布局文件,這個沒什麼,貼上代碼：
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:andro
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ProgressBar
android:
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ProgressBar>
<TextView
android:
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<ProgressBar
android:
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ProgressBar>
<TextView
android:
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</LinearLayout>
然後是配置文件，上代碼：
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:andro
package="sms.down"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="9" />
<application
android:icon="@drawable/icon"
android:label="@string/app_name" >
<activity
android:name=".MulThreadDownload"
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>
<!-- 訪問 internet 權限 -->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CALL_PHONE" />
<uses-permission android:name="android.permission.SEND_SMS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
</manifest>
下麵就是實現代碼，代碼中有相應的注釋：
MulThreadDownload.java
package sms.down;
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 android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
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 final String root = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator;
private final String downloadFile = "https://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";
private final String downloadFile1 = "https://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.main);
this.pb1 = (ProgressBar) this.findViewById(R.id.progressBar1);
this.tv1 = (TextView) this.findViewById(R.id.textView1);
this.pb2 = (ProgressBar) this.findViewById(R.id.progressBar2);
this.tv2 = (TextView) this.findViewById(R.id.textView2);
this.download(this.downloadFile, this.root, this.pb1, this.tv1);
this.download(this.downloadFile1, this.root, this.pb2, this.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 final ProgressBar progressBar;
private final 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;
}
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 final 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;
this.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) {
e.printStackTrace();
}
}
try {
URL fileUrl = new URL(this.url);
HttpURLConnection conn = (HttpURLConnection) fileUrl.openConnection();
// 獲取文件大小
this.size = conn.getContentLength();
InputStream is = conn.getInputStream();
OutputStream os = new FileOutputStream(targetFileName);
while ((this.len = is.read(this.buffer)) != -1) {
os.write(this.buffer);
this.hasDownload += this.len;
this.rate = (this.hasDownload * 100 / this.size);
this.msg = new Message();
this.msg.arg1 = this.rate;
this.myHandler.sendMessage(this.msg);
System.out.println(this.rate + "%");
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
MyThreadTest.java
package sms.down;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ProgressBar;
import android.widget.TextView;
public class MyThreadTest extends Activity {
private ProgressBar pb1 = null;
private TextView tv1 = null;
private Handler handler = null;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.main);
this.pb1 = (ProgressBar) this.findViewById(R.id.progressBar1);
this.tv1 = (TextView) this.findViewById(R.id.textView1);
handler = new Handler() {
public void handleMessage(Message msg) {
pb1.setProgress(msg.arg1);
tv1.setText(msg.arg1 + "%");
switch (msg.arg1) {
case 100:
tv1.setText("下載完成!!");
break;
}
super.handleMessage(msg);
}
};
Runnable runnable = new Runnable() {
int i = 0;
public void run() {
while (i != 100) {
i = i + 10;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Message message = new Message();
message.arg1 = i;
handler.sendMessage(message);
}
}
};
new Thread(runnable).start();
}
}
下麵上一張真機效果圖：
源碼下載地址：https://download.csdn.net/detail/gulaer/5004954 源碼中包含"android 之斷點續傳詳解三部曲之[二] → 斷點續傳下載"和"android 之斷點續傳詳解三部曲之[三] → 多任務同時下載"代碼.
原文地址：https://blog.csdn.net/shimiso/article/details/6763986 非常感謝原作者.
最後更新：2017-04-04 07:03:38