android-断点下载

最新推荐文章于 2023-04-22 15:52:59 发布

原创最新推荐文章于 2023-04-22 15:52:59 发布 · 1.8k 阅读

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<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <EditText 
        android:id="@+id/path"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="@string/path"
        />
     <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
         >
         <Button 
             android:id="@+id/button1"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/button1"
             />
    </LinearLayout>
 
     <ProgressBar
         android:id="@+id/progressBar"
         style="?android:attr/progressBarStyleHorizontal"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />
     <TextView 
         android:id="@+id/progress"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         />
 
     
 
</LinearLayout>

package com.example.dowload;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
	private EditText path = null;
	private static Button start = null;
	private static ProgressBar progressBar = null;
	private static TextView progress = null;
	public static int threadCount = 3;
	public static int runningThread = 3;
	public static final int DOWNLOAD_ERROR = 1;
	public static final int SERVER_ERROR = 2;
	public static final int FINISH = 3;
	public static final int PUDATE = 4;
	public static int length; // 资源总长度
	public static int currentProgress = 0;
	private Handler handler = new Handler() {

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case DOWNLOAD_ERROR:
				Toast.makeText(getApplicationContext(), "下载失败", 1).show();
				break;
			case SERVER_ERROR:
				Toast.makeText(getApplicationContext(), "服务器错误", 1).show();
				break;
			case FINISH:
				Toast.makeText(getApplicationContext(), "下载完成", 1).show();
				start.setEnabled(true);
				break;
			case PUDATE:
				progress.setText("下载完成：" + currentProgress * 100 / length + "%"); // 子线程不可修改ui
				break;
			}
		}
	};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		// 获取组件
		path = (EditText) findViewById(R.id.path);
		start = (Button) findViewById(R.id.button1);
		progressBar = (ProgressBar) findViewById(R.id.progressBar);
		progress = (TextView) findViewById(R.id.progress);
		path.setText("http://192.168.1.102:8080/WEB/olay.avi");
		start.setOnClickListener(new StartClickListenerImpl());
	}

	/**
	 * 下载
	 * 
	 * @param view
	 */
	public void download(View view) {
		final String urlpath = path.getText().toString();
		if (TextUtils.isEmpty(urlpath)) {
			Toast.makeText(MainActivity.this, "下载路径错误", 2).show();
		}
		new Thread() {
			public void run() {
				try {
					// 1 获取服务器，获取一个文件，获取文件的长度，在本地创建一个大小跟服务器文件一样大的临时文件
					// String
					// path="http://192.168.1.102:8080/WEB/olay.avi";//下载路径
					// 这里是web项目中的
					URL url = new URL(urlpath);
					HttpURLConnection conn = (HttpURLConnection) url
							.openConnection();
					conn.setConnectTimeout(5000);
					conn.setRequestMethod("GET");
					int code = conn.getResponseCode();
					if (code == 200) {
						length = conn.getContentLength();
						progressBar.setMax(length);// 设置进度条的最大值
						System.out.println("文件总长度" + length);
						// 在客户端本地创建一个大小跟服务器端资源一样大小的临时文件
						RandomAccessFile raf = new RandomAccessFile(
								"/sdcard/olay.avi", "rwd");
						// 指定创建这个文件的长度
						raf.setLength(length);
						raf.close();
						// 假设是3个线程下载资源
						// 平均每一个线程下载文件的大小
						int blockSize = length / threadCount;
						// 设置每一个线程的起始和末尾的位置
						for (int threadId = 1; threadId <= threadCount; threadId++) {
							// 设置线程下载的开始位置
							int startIndex = (threadId - 1) * blockSize;
							int endIndex = threadId * blockSize - 1;
							if (threadId == threadCount) {// 最后一个线程下载的长度不一样，用公式得不到。但是确定的是endindex=length
								endIndex = length;
							}
							System.out.println("线程：" + threadId + "下载：----"
									+ startIndex + "---->" + endIndex);
							// 在主线程中调用子线程，开始下载
							new DownLoadThread(threadId, startIndex, endIndex,
									urlpath).start();
						}
					} else {
						System.out.println("服务器错误");
						Message msg = new Message();
						msg.what = SERVER_ERROR;
						handler.sendMessage(msg);
					}
				} catch (Exception e) {
					Message msg = new Message();
					msg.what = DOWNLOAD_ERROR;
					handler.sendMessage(msg);
				}
			}
		}.start();
	}

	/**
	 * 下载资源的子线程，每个线程下载对应的对应的资源
	 * 
	 * @author olay
	 * 
	 */
	public class DownLoadThread extends Thread {
		private int threadId, startIndex, endIndex;
		private String path;

		/**
		 * 
		 * @param threadId
		 *            线程id
		 * @param startIndex
		 *            线程下载的开始位置
		 * @param endIndex
		 *            线程下载的结束位置
		 * @param path
		 *            下载路径
		 */
		public DownLoadThread(int threadId, int startIndex, int endIndex,
				String path) {
			this.threadId = threadId;
			this.startIndex = startIndex;
			this.endIndex = endIndex;
			this.path = path;
		}

		@Override
		public void run() {
			try {
				// 检查是否存在记录下载长度的文件，如果存在就读取这个文件的数据
				File tempFile = new File("/sdcard/" + threadId + ".txt");// 创建仔资源的临时文件
				long i = tempFile.length();
				if (tempFile.exists() && tempFile.length() > 0) {// 临时文件存在并且不为空
					FileInputStream fis = new FileInputStream(tempFile);// 创建文件输入流
					byte[] temp = new byte[1024];// 创建缓冲区
					int leng = fis.read(temp);// 读取到文件输入流中
					String downloadlenLong = new String(temp, 0, leng);
					int downloadlenInt = Integer.valueOf(downloadlenLong);
					int alreadydownint = downloadlenInt - startIndex;
					currentProgress += alreadydownint;// 计算上次断点已经下载的长度
					startIndex = downloadlenInt;// 下载后突然断开，第二次下载开始位置为第一次下载完后继续下载
					fis.close();
				} else {
					System.out.println("文件不存在");
				}
				URL url = new URL(path);
				HttpURLConnection conn = (HttpURLConnection) url
						.openConnection();
				conn.setConnectTimeout(5000);
				conn.setRequestMethod("GET");
				// 重要：请求服务器下载部分的文件 指定文件的下载位置
				conn.setRequestProperty("Range", "bytes-" + startIndex + "-"
						+ endIndex);
				int code = conn.getResponseCode();// 从服务器请求全部资源成功的响应码是200，而从服务器请求部分资源成功的响应码是206
				InputStream is = conn.getInputStream();// 返回当前位置对应的文件的输入流
				RandomAccessFile raf = new RandomAccessFile("/sdcard/olay.avi",
						"rwd");
				// 随机写文件的时候从哪个位置开始写
				raf.seek(startIndex);// 定位文件
				// 写入内存
				int len = 0;
				byte[] buffer = new byte[1024];// 声明缓冲区
				int total = 0; // 已经下载的数据长度
				while ((len = is.read(buffer)) != -1) {
					raf.write(buffer, 0, len);// 写入到临时文件
					total += len;
					System.out.println("线程" + threadId + "total:" + total);
					RandomAccessFile file = new RandomAccessFile("/sdcard/"
							+ threadId + ".txt", "rwd");// 记录当前下载记录的长度
					file.write((total + startIndex + "").getBytes());// 帮已经下载的字节写到对应的file文件中
					file.close(); // 记得关RandomAccessFile，不然删除不了文件
					synchronized (MainActivity.class) {
						currentProgress += len; // 获取当前的总进度
						// 特殊情况： 进度条对话框可以在子线程里面更改ui，因为内部做了特殊处理
						progressBar.setProgress(currentProgress);// 更改界面ProgressBar进度条的进度
						// 显示已经下载的比例
						// progress.setText("下载完成："+currentProgress*100/length+"%");
						// 子线程不可修改ui
						Message msg = Message.obtain(); // 消息池：不用重复new Message
														// ，提到效率
						msg.what = PUDATE;
						handler.sendMessage(msg);
					}
				}
				is.close();
				raf.close();
				System.out.println("线程" + threadId + "下载完毕...");
			} catch (Exception e) {
				e.printStackTrace();
			} finally {
				finish();
			}
		}

		private synchronized void finish() {
			runningThread--;
			if (runningThread == 0) { // 全部线程下载完成
				System.out.println("开始删除记录文件");
				for (int i = 1; i <= 3; i++) {
					File file = new File("/sdcard/" + i + ".txt");
					if (file.exists()) {
						if (file.delete()) {
							System.out.println("删除" + i + ".txt文件成功");
						}
					}
				}
				Message msg = new Message();
				msg.what = FINISH;
				handler.sendMessage(msg);
			}
		}
	}

	private class StartClickListenerImpl implements View.OnClickListener {

		@Override
		public void onClick(View v) {
			start.setEnabled(false);
			download(v);
		}
	}

}