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 Android教程網 >> Android技術 >> 關於Android編程 >> Android開發--多線程下載加斷點續傳

Android開發--多線程下載加斷點續傳

日期:2017/2/23 16:11:48      編輯:關於Android編程

文件下載在App應用中也用到很多,一般版本更新時多要用的文件下載來進行處理,以前也有看過很多大神有過該方面的博客,今天我也自己來實踐一下,寫的一般,還請大家多提意見,共同進步。主要思路:

1.多線程下載:

首先通過下載總線程數來劃分文件的下載區域:利用int range = fileSize / threadCount;得到每一段下載量;每一段的位置是i * range到(i + 1) * rang - 1,注意最後一段的位置是到filesize - 1;

通過Http協議的Range字段實現下載文件的分段;

通過Java類RandomAccessFile可以實現文件的隨機訪問,利用seek方法定位的文件的指定位置;

由HttpUrlConnection獲取流來進行流的讀寫,實現文件的存儲;

在下載過程中利用Handler來向外傳遞下載的信息。

2.斷點續傳:

對於每一個線程利用一個DownloadInfo類來保存下載的信息,每次在下載過程中向數據庫更新信息(我也有想過只在下載暫停時進行更新,但那樣的話我們的進程被殺掉時信息就無法保存下來)。在進行下載之前去訪問數據庫是否有記錄存在,如果沒有執行第一次下載的初始化,如果存在記錄但下載文件不存在時,刪掉數據庫中的記錄之後進行第一次下載的初始化,如果有記錄且文件存在,則從數據庫中取出信息。

實現的效果如圖,自己封裝的類提供了開始,暫停,刪除,以及重新下載的方法。還沒來得及將工程穿上CSDN,給大家一個百度雲盤的下載地址:http://pan.baidu.com/s/1dD1Xo8T

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主要類的結構有:

1)DownloadHttpTool:利用Http協議進行網絡下載類<喎?/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+ICAgICAgICAgICAgICAgICAgICAgMqOpRG93bmxhb2RTcWxUb29so6wgRG93bkxvYWRIZWxwZXKjusr9vt2/4s/gudiy2df3wOA8L3A+CjxwPiAgICAgICAgICAgICAgICAgICAgIDOjqURvd25sb2FkSW5mb6O6z8LU2NDFz6Kxo7TmwOA8L3A+CjxwPiAgICAgICAgICAgICAgICAgICAgIDSjqURvd25sb2FkVXRpbKO6t+LXsM/C1Ni3vbeosqLM4bmpttTN4r3Tv9q1xMDgPGJyPgo8L3A+CjxwPiDM+dK7z8K0+sLro7pEb3dubG9hZEluZm/A4DxwcmUgY2xhc3M9"brush:java;">package com.example.test; public class DownloadInfo { /** * 保存每個下載線程下載信息類 * */ private int threadId;// 下載器id private int startPos;// 開始點 private int endPos;// 結束點 private int compeleteSize;// 完成度 private String url;// 下載文件的URL地址 public DownloadInfo(int threadId, int startPos, int endPos, int compeleteSize, String url) { this.threadId = threadId; this.startPos = startPos; this.endPos = endPos; this.compeleteSize = compeleteSize; this.url = url; } public DownloadInfo() { } public String getUrl() { return url; } public void setUrl(String url) { this.url = url; } public int getThreadId() { return threadId; } public void setThreadId(int threadId) { this.threadId = threadId; } public int getStartPos() { return startPos; } public void setStartPos(int startPos) { this.startPos = startPos; } public int getEndPos() { return endPos; } public void setEndPos(int endPos) { this.endPos = endPos; } public int getCompeleteSize() { return compeleteSize; } public void setCompeleteSize(int compeleteSize) { this.compeleteSize = compeleteSize; } @Override public String toString() { return "DownloadInfo [threadId=" + threadId + ", startPos=" + startPos + ", endPos=" + endPos + ", compeleteSize=" + compeleteSize + "]"; } } DownLoadHelper類,創建我們的數據庫文件

package com.example.test;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * 利用數據庫來記錄下載信息
 * @author acer
 */
public class DownLoadHelper extends SQLiteOpenHelper{

	private static final String SQL_NAME = "download.db";
	private static final int DOWNLOAD_VERSION=1;
	
	public DownLoadHelper(Context context) {
		super(context, SQL_NAME, null, DOWNLOAD_VERSION);
		// TODO Auto-generated constructor stub
	}
	
	 /**
     * 在download.db數據庫下創建一個download_info表存儲下載信息
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table download_info(_id integer PRIMARY KEY AUTOINCREMENT, thread_id integer, "
                + "start_pos integer, end_pos integer, compelete_size integer,url char)");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

}
DownlaodSqlTool進行數據的插入更新刪除等操作
package com.example.test;

import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

/**
 * 
 * 數據庫操作工具類
 */
public class DownlaodSqlTool {
    private DownLoadHelper dbHelper;

    public DownlaodSqlTool(Context context) {
        dbHelper = new DownLoadHelper(context);
    }

    /**
     * 創建下載的具體信息
     */
    public void insertInfos(List infos) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        for (DownloadInfo info : infos) {
            String sql = "insert into download_info(thread_id,start_pos, end_pos,compelete_size,url) values (?,?,?,?,?)";
            Object[] bindArgs = { info.getThreadId(), info.getStartPos(),
                    info.getEndPos(), info.getCompeleteSize(), info.getUrl() };
            database.execSQL(sql, bindArgs);
        }
    }

    /**
     * 得到下載具體信息
     */
    public List getInfos(String urlstr) {
        List list = new ArrayList();
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        String sql = "select thread_id, start_pos, end_pos,compelete_size,url from download_info where url=?";
        Cursor cursor = database.rawQuery(sql, new String[] { urlstr });
        while (cursor.moveToNext()) {
            DownloadInfo info = new DownloadInfo(cursor.getInt(0),
                    cursor.getInt(1), cursor.getInt(2), cursor.getInt(3),
                    cursor.getString(4));
            list.add(info);
        }
        return list;
    }

    /**
     * 更新數據庫中的下載信息
     */
    public void updataInfos(int threadId, int compeleteSize, String urlstr) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        String sql = "update download_info set compelete_size=? where thread_id=? and url=?";
        Object[] bindArgs = { compeleteSize, threadId, urlstr };
        database.execSQL(sql, bindArgs);
    }
    /**
     * 關閉數據庫
     */
    public void closeDb() {
        dbHelper.close();
    }

    /**
     * 下載完成後刪除數據庫中的數據
     */
    public void delete(String url) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        database.delete("download_info", "url=?", new String[] { url });
    }
}
DownloadHttpTool進行網絡下載的類
package com.example.test;

import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

public class DownloadHttpTool {
	/**
	 * 
	 * 利用Http協議進行多線程下載具體實踐類
	 */

	private static final String TAG = DownloadHttpTool.class.getSimpleName();

	private int threadCount;//線程數量
	private String urlstr;//URL地址
	private Context mContext;
	private Handler mHandler;
	private List downloadInfos;//保存下載信息的類

	private String localPath;//目錄
	private String fileName;//文件名
	private int fileSize;
	private DownlaodSqlTool sqlTool;//文件信息保存的數據庫操作類

	private enum Download_State {
		Downloading, Pause, Ready;//利用枚舉表示下載的三種狀態
	}

	private Download_State state = Download_State.Ready;//當前下載狀態

	private int globalCompelete = 0;//所有線程下載的總數

	public DownloadHttpTool(int threadCount, String urlString,
			String localPath, String fileName, Context context, Handler handler) {
		super();
		this.threadCount = threadCount;
		this.urlstr = urlString;
		this.localPath = localPath;
		this.mContext = context;
		this.mHandler = handler;
		this.fileName = fileName;
		sqlTool = new DownlaodSqlTool(mContext);
	}

	//在開始下載之前需要調用ready方法進行配置
	public void ready() {
		Log.w(TAG, "ready");
		globalCompelete = 0;
		downloadInfos = sqlTool.getInfos(urlstr);
		if (downloadInfos.size() == 0) {
			initFirst();
		} else {
			File file = new File(localPath + "/" + fileName);
			if (!file.exists()) {
				sqlTool.delete(urlstr);
				initFirst();
			} else {
				fileSize = downloadInfos.get(downloadInfos.size() - 1)
						.getEndPos();
				for (DownloadInfo info : downloadInfos) {
					globalCompelete += info.getCompeleteSize();
				}
				Log.w(TAG, "globalCompelete:::" + globalCompelete);
			}
		}
	}

	public void start() {
		Log.w(TAG, "start");
		if (downloadInfos != null) {
			if (state == Download_State.Downloading) {
				return;
			}
			state = Download_State.Downloading;
			for (DownloadInfo info : downloadInfos) {
				Log.v(TAG, "startThread");
				new DownloadThread(info.getThreadId(), info.getStartPos(),
						info.getEndPos(), info.getCompeleteSize(),
						info.getUrl()).start();
			}
		}
	}

	public void pause() {
		state = Download_State.Pause;
		sqlTool.closeDb();
	}
	
	public void delete(){
		compelete();
		File file = new File(localPath + "/" + fileName);
		file.delete();
	}
	
	public void compelete() {
		sqlTool.delete(urlstr);
		sqlTool.closeDb();
	}

	public int getFileSize() {
		return fileSize;
	}

	public int getCompeleteSize() {
		return globalCompelete;
	}

	//第一次下載初始化
	private void initFirst() {
		Log.w(TAG, "initFirst");
		try {
			URL url = new URL(urlstr);
			HttpURLConnection connection = (HttpURLConnection) url
					.openConnection();
			connection.setConnectTimeout(5000);
			connection.setRequestMethod("GET");
			fileSize = connection.getContentLength();
			Log.w(TAG, "fileSize::" + fileSize);
			File fileParent = new File(localPath);
			if (!fileParent.exists()) {
				fileParent.mkdir();
			}
			File file = new File(fileParent, fileName);
			if (!file.exists()) {
				file.createNewFile();
			}
			// 本地訪問文件
			RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");
			accessFile.setLength(fileSize);
			accessFile.close();
			connection.disconnect();
		} catch (Exception e) {
			e.printStackTrace();
		}
		int range = fileSize / threadCount;
		downloadInfos = new ArrayList();
		for (int i = 0; i < threadCount - 1; i++) {
			DownloadInfo info = new DownloadInfo(i, i * range, (i + 1) * range
					- 1, 0, urlstr);
			downloadInfos.add(info);
		}
		DownloadInfo info = new DownloadInfo(threadCount - 1, (threadCount - 1)
				* range, fileSize - 1, 0, urlstr);
		downloadInfos.add(info);
		sqlTool.insertInfos(downloadInfos);
	}

	//自定義下載線程
	private class DownloadThread extends Thread {

		private int threadId;
		private int startPos;
		private int endPos;
		private int compeleteSize;
		private String urlstr;
		private int totalThreadSize;

		public DownloadThread(int threadId, int startPos, int endPos,
				int compeleteSize, String urlstr) {
			this.threadId = threadId;
			this.startPos = startPos;
			this.endPos = endPos;
			totalThreadSize = endPos - startPos + 1;
			this.urlstr = urlstr;
			this.compeleteSize = compeleteSize;
		}

		@Override
		public void run() {
			HttpURLConnection connection = null;
			RandomAccessFile randomAccessFile = null;
			InputStream is = null;
			try {
				randomAccessFile = new RandomAccessFile(localPath + "/"
						+ fileName, "rwd");
				randomAccessFile.seek(startPos + compeleteSize);
				URL url = new URL(urlstr);
				connection = (HttpURLConnection) url.openConnection();
				connection.setConnectTimeout(5000);
				connection.setRequestMethod("GET");
				connection.setRequestProperty("Range", "bytes="
						+ (startPos + compeleteSize) + "-" + endPos);
				is = connection.getInputStream();
				byte[] buffer = new byte[1024];
				int length = -1;
				while ((length = is.read(buffer)) != -1) {
					randomAccessFile.write(buffer, 0, length);
					compeleteSize += length;
					Message message = Message.obtain();
					message.what = threadId;
					message.obj = urlstr;
					message.arg1 = length;
					mHandler.sendMessage(message);
					sqlTool.updataInfos(threadId, compeleteSize, urlstr);
					Log.w(TAG, "Threadid::" + threadId + "    compelete::"
							+ compeleteSize + "    total::" + totalThreadSize);
					if (compeleteSize >= totalThreadSize) {
						break;
					}
					if (state != Download_State.Downloading) {
						break;
					}
				}

			} catch (Exception e) {
				e.printStackTrace();
			} finally {
				try {
					if (is != null) {
						is.close();
					}
					randomAccessFile.close();
					connection.disconnect();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}
}
DownloadUtils提供下載向外接口方法類:
package com.example.test;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

/**
 * 將下載方法封裝在此類
 * 提供下載,暫停,刪除,以及重置的方法
 */
public class DownloadUtil {

	private DownloadHttpTool mDownloadHttpTool;
	private OnDownloadListener onDownloadListener;

	private int fileSize;
	private int downloadedSize = 0;

	@SuppressLint("HandlerLeak")
	private Handler mHandler = new Handler() {

		@Override
		public void handleMessage(Message msg) {
			// TODO Auto-generated method stub
			super.handleMessage(msg);
			int length = msg.arg1;
			synchronized (this) {//加鎖保證已下載的正確性
				downloadedSize += length;
			}
			if (onDownloadListener != null) {
				onDownloadListener.downloadProgress(downloadedSize);
			}
			if (downloadedSize >= fileSize) {
				mDownloadHttpTool.compelete();
				if (onDownloadListener != null) {
					onDownloadListener.downloadEnd();
				}
			}
		}

	};

	public DownloadUtil(int threadCount, String filePath, String filename,
			String urlString, Context context) {

		mDownloadHttpTool = new DownloadHttpTool(threadCount, urlString,
				filePath, filename, context, mHandler);
	}

	//下載之前首先異步線程調用ready方法獲得文件大小信息,之後調用開始方法
	public void start() {
		new AsyncTask() {

			@Override
			protected Void doInBackground(Void... arg0) {
				// TODO Auto-generated method stub
				mDownloadHttpTool.ready();
				return null;
			}

			@Override
			protected void onPostExecute(Void result) {
				// TODO Auto-generated method stub
				super.onPostExecute(result);
				fileSize = mDownloadHttpTool.getFileSize();
				downloadedSize = mDownloadHttpTool.getCompeleteSize();
				Log.w("Tag", "downloadedSize::" + downloadedSize);
				if (onDownloadListener != null) {
					onDownloadListener.downloadStart(fileSize);
				}
				mDownloadHttpTool.start();
			}
		}.execute();
	}

	public void pause() {
		mDownloadHttpTool.pause();
	}
	
	public void delete(){
		mDownloadHttpTool.delete();
	}

	public void reset(){
		mDownloadHttpTool.delete();
		start();
	}
	
	public void setOnDownloadListener(OnDownloadListener onDownloadListener) {
		this.onDownloadListener = onDownloadListener;
	}

	//下載回調接口
	public interface OnDownloadListener {
		public void downloadStart(int fileSize);

		public void downloadProgress(int downloadedSize);//記錄當前所有線程下總和

		public void downloadEnd();
	}
}
在MainActivity
package com.example.test;

import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.example.test.DownloadUtil.OnDownloadListener;

public class MainActivity extends FragmentActivity {

	private static final String TAG = MainActivity.class.getSimpleName();

	private ProgressBar mProgressBar;
	private Button start;
	private Button pause;
	private Button delete;
	private Button reset;
	private TextView total;

	private int max;

	private DownloadUtil mDownloadUtil;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		mProgressBar = (ProgressBar) findViewById(R.id.progressBar1);
		start = (Button) findViewById(R.id.button_start);
		pause = (Button) findViewById(R.id.button_pause);
		delete = (Button) findViewById(R.id.button_delete);
		reset = (Button) findViewById(R.id.button_reset);
		total = (TextView) findViewById(R.id.textView_total);
		String urlString = "http://bbra.cn/Uploadfiles/imgs/20110303/fengjin/013.jpg";
		String localPath = Environment.getExternalStorageDirectory()
				.getAbsolutePath() + "/local";
		mDownloadUtil = new DownloadUtil(2, localPath, "abc.jpg", urlString,
				this);
		mDownloadUtil.setOnDownloadListener(new OnDownloadListener() {

			@Override
			public void downloadStart(int fileSize) {
				// TODO Auto-generated method stub
				Log.w(TAG, "fileSize::" + fileSize);
				max = fileSize;
				mProgressBar.setMax(fileSize);
			}

			@Override
			public void downloadProgress(int downloadedSize) {
				// TODO Auto-generated method stub
				Log.w(TAG, "Compelete::" + downloadedSize);
				mProgressBar.setProgress(downloadedSize);
				total.setText((int) downloadedSize * 100 / max + "%");
			}

			@Override
			public void downloadEnd() {
				// TODO Auto-generated method stub
				Log.w(TAG, "ENd");
			}
		});
		start.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				mDownloadUtil.start();
			}
		});
		pause.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				mDownloadUtil.pause();
			}
		});
		delete.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				mDownloadUtil.delete();
			}
		});
		reset.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				mDownloadUtil.reset();
			}
		});
	}

}






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