同理,只需要把第十九课的代码搬至android代码中改造一下即可完成,且完善进度条功能
public class MainActivity extends Activity {
int ThreadCount = 4;
String fileName = "nopad.zip";
String path = "http://192.168.1.103:8080/android/" + fileName;
int finishedThread = 0;
int currentProgress;
ProgressBar pb;
Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == 0) {
Toast.makeText(MainActivity.this, "下载完成了", 0).show();
}
};
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pb = (ProgressBar) findViewById(R.id.pb);
}
public void startDown(View v) {
currentProgress = 0;
Toast.makeText(this, "开始下载了", 0).show();
Thread t = new Thread() {
@Override
public void run() {
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
if (conn.getResponseCode() == 200) {
// 1.先获取请求资源的大小
int length = conn.getContentLength();
pb.setMax(length); // 设置进度条的最大值
File file = new File(
Environment.getExternalStorageDirectory(),
fileName);
// 生成临时文件
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
// 设置临时文件的大小
raf.setLength(length);
raf.close();
// 计算每个线程应该要下载多少个字节
int size = length / ThreadCount;
for (int i = 0; i < ThreadCount; i++) {
// 计算线程下载的开始位置和结束位置
int startIndex = i * size;
int endIndex = (i + 1) * size - 1;
// 如果是最后一个线程,那么结束位置写死
if (i == (ThreadCount - 1)) {
endIndex = length - 1;
}
new DownThread(startIndex, endIndex, i).start();
}
}
} catch (IOException e) {
}
}
};
t.start();
}
class DownThread extends Thread {
int startIndex;
int endIndex;
int threadId;
public DownThread(int startIndex, int endIndex, int threadId) {
super();
this.startIndex = startIndex;
this.endIndex = endIndex;
this.threadId = threadId;
}
@Override
public void run() {
// 再次发送HTTP请求,下载源文件
try {
// 生成一个专门用来记录下载进度的临时文件
File progressFile = new File(
Environment.getExternalStorageDirectory(), threadId
+ ".txt");
if (progressFile.exists()) {
FileInputStream fis = new FileInputStream(progressFile);
BufferedReader br = new BufferedReader(
new InputStreamReader(fis));
int lastProgress = Integer.parseInt(br.readLine());
// 从进度临时文件中读取出上一次下载的总进度,然后与原本的开始位置相加,得到新的开始位置
startIndex += lastProgress;
currentProgress += lastProgress;
pb.setProgress(currentProgress);
fis.close();
}
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
System.out.println("线程threadId" + threadId + "下载区间:"
+ startIndex + "-" + endIndex);
// 设置请求的数据的区间
conn.setRequestProperty("Range", "bytes=" + startIndex + "-"
+ endIndex);
// 请求部分数据,响应码为206
if (conn.getResponseCode() == 206) {
// 此时只有 1/threadcount数据
InputStream is = conn.getInputStream();
byte[] b = new byte[1024];
int len = 0;
long total = 0;
File file = new File(
Environment.getExternalStorageDirectory(), fileName);
// 这样可以保证数据同步写入硬盘中,防止停电等原因da
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
// 把文件的写入位置移动至startIndex
raf.seek(startIndex);
while ((len = is.read(b)) != -1) {
// 每次读取流里的数据写入临时文件
raf.write(b, 0, len);
total += len;
currentProgress += len;
pb.setProgress(currentProgress);
System.out.println("线程" + threadId + " 下载了:" + total);
RandomAccessFile progressRaf = new RandomAccessFile(
progressFile, "rwd");
progressRaf.write((total + "").getBytes());
progressRaf.close();
}
raf.close();
progressFile.delete(); // 下载完成后,将临时文件删除
++finishedThread;
synchronized (path) {
if (finishedThread == ThreadCount) {
handler.sendEmptyMessage(0);
for (int i = 0; i < ThreadCount; i++) {
File f = new File(
Environment
.getExternalStorageDirectory(),
i + ".txt");
f.delete();
}
finishedThread = 0;
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
布局文件:
<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"
tools:context="com.example.multidown.MainActivity" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="startDown"
android:text="开始下载" />
<ProgressBar
android:id="@+id/pb"
style="@android:style/Widget.ProgressBar.Horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
效果图:
[图片上传中。。。（1）]
