android（25）（android下实现多线程断点下载）

1.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=".MainActivity" >

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="请输入下载文件的路径" />

<EditText
android:id="@+id/et_path"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="http://192.168.1.100:8080/" />

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="请输入线程的数量" />

<EditText
android:id="@+id/et_count"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:inputType="number"
android:text="3" />

<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="downLoad"
android:text="下载" />

<LinearLayout
android:id="@+id/ll_container"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</LinearLayout>

</LinearLayout>
进度条的布局：
<?xml version="1.0" encoding="utf-8"?>
<ProgressBar xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
业务逻辑代码的实现：
public class MainActivity extends Activity {
protected static final int DOWNLOAD_ERROR = 1;//下载错误
private static final int THREAD_ERROR = 2;//线程数量错误
public static final int DWONLOAD_FINISH = 3;//下载完毕
private EditText et_path;//url路径
private EditText et_count;//线程数量
/**
* 存放进度条的布局
*/
private LinearLayout ll_container;

/**
* 进度条的集合
*/
private List<ProgressBar> pbs;

/**
* android下的消息处理器，在主线程创建，才可以更新ui
*/
private Handler handler = new Handler(){
public void handleMessage(Message msg) {
switch (msg.what) {
case DOWNLOAD_ERROR:
Toast.makeText(getApplicationContext(), "下载失败", 0).show();
break;
case THREAD_ERROR:
Toast.makeText(getApplicationContext(), "下载失败,请重试", 0).show();
break;
case DWONLOAD_FINISH:
Toast.makeText(getApplicationContext(), "下载完成", 0).show();
break;
}
};
};

/**
* 线程的数量
*/
private int threadCount = 3;

/**
* 每个下载区块的大小
*/
private long blocksize;

/**
* 正在运行的线程的数量
*/
private  int runningThreadCount;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_path = (EditText) findViewById(R.id.et_path);
et_count = (EditText) findViewById(R.id.et_count);
ll_container = (LinearLayout) findViewById(R.id.ll_container);
}

/**
* 下载按钮的点击事件
* @param view
*/
public void downLoad(View view){
//下载文件的路径
final String path = et_path.getText().toString().trim();
if(TextUtils.isEmpty(path)){
Toast.makeText(this, "对不起下载路径不能为空", 0).show();
return;
}
//开启线程的数量
String count = et_count.getText().toString().trim();
if(TextUtils.isEmpty(path)){
Toast.makeText(this, "对不起,线程数量不能为空", 0).show();
return;
}
threadCount = Integer.parseInt(count);
//清空掉旧的进度条（线性布局清理掉所有的视图）
ll_container.removeAllViews();
//在界面里面添加count个进度条
pbs = new ArrayList<ProgressBar>();
for(int j=0;j<threadCount;j++){
ProgressBar pb = (ProgressBar) View.inflate(this, R.layout.pb, null);
ll_container.addView(pb);//把进度条添加到现行布局的容器中
pbs.add(pb);//把进度条添加到进度条集合中。
}
Toast.makeText(this, "开始下载", 0).show();
new Thread(){
public void run() {
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
int code = conn.getResponseCode();
if (code == 200) {
long size = conn.getContentLength();// 得到服务端返回的文件的大小
System.out.println("服务器文件的大小：" + size);
blocksize = size / threadCount;
// 1.首先在本地创建一个大小跟服务器一模一样的空白文件。
File file = new File(Environment.getExternalStorageDirectory(),getFileName(path));
RandomAccessFile raf = new RandomAccessFile(file, "rw");
raf.setLength(size);
// 2.开启若干个子线程分别去下载对应的资源。
runningThreadCount = threadCount;
for (int i = 1; i <= threadCount; i++) {
long startIndex = (i - 1) * blocksize;
long endIndex = i * blocksize - 1;
if (i == threadCount) {
// 最后一个线程
endIndex = size - 1;
}
System.out.println("开启线程：" + i + "下载的位置：" + startIndex + "~"
+ endIndex);
int threadSize = (int) (endIndex - startIndex);
pbs.get(i-1).setMax(threadSize);
new DownloadThread(path, i, startIndex, endIndex).start();
}
}
conn.disconnect();
} catch (Exception e) {
e.printStackTrace();
Message msg = Message.obtain();
msg.what = DOWNLOAD_ERROR;
handler.sendMessage(msg);
}

};
}.start();

}
private class DownloadThread extends Thread {

private int threadId;
private long startIndex;
private long endIndex;
private String path;

public DownloadThread(String path, int threadId, long startIndex,
long endIndex) {
this.path = path;
this.threadId = threadId;
this.startIndex = startIndex;
this.endIndex = endIndex;
}

@Override
public void run() {
try {
// 当前线程下载的总大小
int total = 0;
//下载的进度信息存储到一个文本文件中。以线程id命名。
File positionFile = new File(Environment.getExternalStorageDirectory(),getFileName(path)+threadId + ".txt");
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setRequestMethod("GET");
// 接着从上一次的位置继续下载数据
if (positionFile.exists() && positionFile.length() > 0) {// 判断是否有记录
FileInputStream fis = new FileInputStream(positionFile);
BufferedReader br = new BufferedReader(
new InputStreamReader(fis));
// 获取当前线程上次下载的总大小是多少
String lasttotalstr = br.readLine();
int lastTotal = Integer.valueOf(lasttotalstr);
System.out.println("上次线程" + threadId + "下载的总大小："
+ lastTotal);
startIndex += lastTotal;
total += lastTotal;// 加上上次下载的总大小。
fis.close();
//存数据库。
//_id path threadid total
}

conn.setRequestProperty("Range", "bytes=" + startIndex + "-"
+ endIndex);

conn.setConnectTimeout(5000);
int code = conn.getResponseCode();
System.out.println("code=" + code);
InputStream is = conn.getInputStream();
File file = new File(Environment.getExternalStorageDirectory(),getFileName(path));
RandomAccessFile raf = new RandomAccessFile(file, "rw");
// 指定文件开始写的位置。
raf.seek(startIndex);
System.out.println("第" + threadId + "个线程：写文件的开始位置："
+ String.valueOf(startIndex));
int len = 0;
byte[] buffer = new byte[1024];
while ((len = is.read(buffer)) != -1) {
RandomAccessFile rf = new RandomAccessFile(positionFile,
"rwd");
raf.write(buffer, 0, len);
total += len;
rf.write(String.valueOf(total).getBytes());
rf.close();
pbs.get(threadId-1).setProgress(total);
}
is.close();
raf.close();

} catch (Exception e) {
e.printStackTrace();
Message msg = Message.obtain();
msg.what = THREAD_ERROR;
handler.sendMessage(msg);
} finally {
// 只有所有的线程都下载完毕后 才可以删除记录文件。
synchronized (MainActivity.class) {
System.out.println("线程" + threadId + "下载完毕了");
runningThreadCount--;
if (runningThreadCount < 1) {
System.out.println("所有的线程都工作完毕了。删除临时记录的文件");
for (int i = 1; i <= threadCount; i++) {
File f = new File(Environment.getExternalStorageDirectory(),getFileName(path)+ i + ".txt");
System.out.println(f.delete());
}
Message msg = Message.obtain();
msg.what = DWONLOAD_FINISH;
handler.sendMessage(msg);
}
}

}
}
}
//http://192.168.1.100:8080/aa.exe
//根据路径名称得到文件名称
private String getFileName(String path){
int start = path.lastIndexOf("/")+1;
return path.substring(start);
}