多线程下载

来源：互联网发布：中文安卓编程开创e4a 编辑：程序博客网时间：2024/06/01 19:56

package com.example.duoxianchengxiazai;

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.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Handler.Callback;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {
private EditText weburl;
private Button btn;
private boolean flag = false;// false暂停下载true正在下载
private int total = 0;// 已下载了的
private File file;
private int end;// 文件的总长度
private List<Map<String, Integer>> list = new ArrayList<Map<String, Integer>>();
private ProgressBar progressBar0;
private Handler handler = new Handler(new Callback() {

@Override
public boolean handleMessage(Message msg) {
// TODO Auto-generated method stub
if (msg.what == 0x123) {
if (msg.arg1 >= end) {
Toast.makeText(MainActivity.this, "下载完成", 1).show();
}
progressBar0.setProgress(msg.arg1);
}
return false;
}
});

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
weburl = (EditText) findViewById(R.id.weburl1);
btn = (Button) findViewById(R.id.uploadbut1);
progressBar0 = (ProgressBar) findViewById(R.id.prog1);
btn.setOnClickListener(this);
}

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (flag) {
flag = false;
btn.setText("下载");
return;
}
flag = true;
btn.setText("暂停");
if (total == 0) {
new Thread() {
public void run() {
try {
file = new File(
Environment.getExternalStorageDirectory()
+ "/file", getFileName(weburl.getText()
.toString()));
URL url = new URL(weburl.getText().toString());
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setConnectTimeout(5000);
end = conn.getContentLength();// 获取文件的长度
progressBar0.setMax(end);
Log.e("TAG", "length:" + end + "=====");
RandomAccessFile accessFile = new RandomAccessFile(
file, "rw");
accessFile.setLength(end);// 设置文件的长度
int addload = end / 4;
for (int i = 0; i < 4; i++) {
int start = i * addload;
int over = (i + 1) * addload;
if (i == 3) {
over = end;
}
Map<String, Integer> map = new HashMap<String, Integer>();
map.put("start", start);
map.put("over", over);
map.put("finished", 0);
list.add(map);
Thread thread = new Thread(new DownLoadd(start,
over, file, i));
thread.start();
}

} catch (IOException e) {
e.printStackTrace();
}
};
}.start();
} else {
// 续传
for (int j = 0; j < list.size(); j++) {
Thread thread = new Thread(new DownLoadd(list.get(j).get(
"start")
+ list.get(j).get("finished"), list.get(j).get("over"),
file, j));
thread.start();
}

}
}

class DownLoadd implements Runnable {
private int begin;// 请求数据的其实位置
private int end;// 请求的结束位置
private File file;
private int id;

DownLoadd(int begin, int end, File file, int id) {
this.begin = begin;
this.end = end;
this.file = file;
this.id = id;
}

public void run() {
try {
URL url = new URL(weburl.getText().toString());
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setConnectTimeout(5000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Range", "bytes=" + begin + "-" + end);
RandomAccessFile accessFile = new RandomAccessFile(file, "rw");
accessFile.seek(begin);
InputStream is = conn.getInputStream();
int len;
byte[] b = new byte[1024 * 1024];
while ((len = is.read(b)) != -1 && flag) {
accessFile.write(b, 0, len);
list.get(id).put("finished",
list.get(id).get("finished") + len);
addFinshed(len);
}
accessFile.close();
is.close();
conn.disconnect();

} catch (Exception e) {
Log.e("url", "url异常");
e.printStackTrace();
}
}

}

synchronized private void addFinshed(int len) {
total += len;// 记录已下载的总长度
Log.e("TAG", "已完成：" + total);
// 发一个数据
handler.obtainMessage(0x123, total, 0).sendToTarget();
}

// 获取下载文件的文件名
private String getFileName(String url) {
int index = url.lastIndexOf("/") + 1;
return url.substring(index);
}

}

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