服务端情况是：http://192.168.1.105:8080:/web/sky.jpg 敲回车，就在浏览器展现图片资源>>>>>>> 服务端代码省略。。。。
down_activity.xml(button是提交网络请求下载图片的，textview是一旦完成下载进行界面提示的)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="下载" />
</LinearLayout>DownLoadActivity
package com.lw.http01;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class DownLoadActivity extends Activity {
private TextView textView;
private Button button;
private int count = 0;
private Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
int result = msg.what;
count += result;
if (count == 3) {
// 完成下载更新ui界面就可以
textView.setText("download success");
}
};
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.down_activity);
textView = (TextView) findViewById(R.id.textView);
button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
/**
* 在子线程中获取网络图片
*/
new Thread() {
public void run() {
DownLoad load = new DownLoad(handler);
load.downLoadFile("http://192.168.1.105:8080:/web/sky.jpg");
};
}.start();
}
});
}
}
DownLoad
package com.lw.http01;
import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
public class DownLoad {
/**
* 创建3个线程的线程池
*/
private Executor threadPool = Executors.newFixedThreadPool(3);
static class DownLoadRunnable implements Runnable {
/**
* 定义传递过来的參数
*/
private String url;
private String fileName;
private long start;
private long end;
private Handler handler;
public DownLoadRunnable(String url, String fileName, long start,
long end, Handler handler) {
super();
this.url = url;
this.fileName = fileName;
this.start = start;
this.end = end;
this.handler = handler;
}
@Override
public void run() {
try {
// 创建url地址，而且设置參数值
URL httpUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) httpUrl
.openConnection();
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
// http协议。请求指定长度的流信息
conn.setRequestProperty("Range", "bytes=" + start + "-" + end);
// 定位写入信息到指定文件文件夹中
RandomAccessFile access = new RandomAccessFile(new File(
fileName), "rwd");
// 去捕捉起始点--将文件记录指针定位到pos位置。
access.seek(start);
// 获取输入路。从server得到文件
InputStream in = conn.getInputStream();
byte[] b = new byte[1024 * 4];
int len = 0;
while ((len = in.read(b)) != -1) {
// 输出
access.write(b, 0, len);
}
if (access != null) {
access.close();
}
if (in != null) {
in.close();
}
// 每一个线程完成下载后，发送消息
Message message = new Message();
message.what = 1;
handler.sendMessage(message);
} catch (Exception e) {
}
}
}
/**
* 定义handler是由于 在DownLoadRunnable中须要有handler发送消息（每一个线程完成下载发送消息。更新主界面）
*/
private Handler handler;
public DownLoad(Handler handler) {
this.handler = handler;
}
public void downLoadFile(String url) {
try {
/**
* 创建url地址信息。而且设置參数
*/
URL httpUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) httpUrl
.openConnection();
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
// 拿到网络资源的整体大小
int count = conn.getContentLength();
// 每一个下载下载的大小
int block = count / 3;
// 获取网路资源的后缀名
String fileName = getFile(url);
// 得到文件夹的根文件夹
File parent = Environment.getExternalStorageDirectory();
// 获取文件的真实绝对路径
File downLoadFile = new File(parent, fileName);
/**
* 11整体大小/3 blcok为3 余2 第一个线程 0-2 第二个线程 3-5 第三个线程 6-10
*/
for (int i = 0; i < 3; i++) {
long start = i * block;
long end = (i + 1) * block - 1;
if (i == 2) {
end = count;
}
/**
* 传递start、end是由于setRequestProperty由于协议须要这2个參数
* url是由于每一个线程下载须要url地址信息 hander是发送消息。更新ui界面
*/
DownLoadRunnable runnable = new DownLoadRunnable(url,
downLoadFile.getAbsolutePath(), start, end, handler);
threadPool.execute(runnable);
}
} catch (Exception e) {
}
}
// 通过url拿到文件的后缀名字
public String getFile(String url) {
return url.substring(url.lastIndexOf("/") + 1);
}
}