本文實例講述了Android編程開發實現帶進度條和百分比的多線程下載。分享給大家供大家參考，具體如下：
繼上一篇《java多線程下載實例詳解》之后，可以將它移植到我們的安卓中來，下面是具體實現源碼：
DownActivity.java：
package com.example.downloads;import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import com.example.downloads.utils.DownLoadThread;import android.os.Bundle;import android.os.Environment;import android.os.Handler;import android.os.Message;import android.annotation.SuppressLint;import android.app.Activity;import android.text.TextUtils;import android.view.Menu;import android.view.View;import android.widget.EditText;import android.widget.ProgressBar;import android.widget.TextView;import android.widget.Toast;public class DownActivity extends Activity { // 聲明控件 // 路徑與線程數量 public EditText et_url, et_num; // 進度條 public static ProgressBar pb_thread; // 顯示進度的操作 public TextView tv_pb; // 線程的數量 public static int threadNum = 3; // 每個線程負責下載的大小 public int blockSize; public static int threadCount;// 數量 // 訪問的path public String path; public static boolean flag = true; // 記錄進度條的值 public static int pb_count = 0; public static Handler handler; public static final int TEXTVALUE = 1; public static int pb_num = 0; public static int size = 0; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_down); et_url = (EditText) findViewById(R.id.et_path); et_num = (EditText) findViewById(R.id.et_threadNum); pb_thread = (ProgressBar) findViewById(R.id.pb_down); tv_pb = (TextView) findViewById(R.id.tv_pb); handler = new Handler() { @SuppressLint("HandlerLeak") @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what) { case TEXTVALUE: System.out.println("-------" + DownActivity.pb_count + "http://////" + DownActivity.size); // 改變TEXTView pb_num = (DownActivity.pb_count * 100) / DownActivity.size; tv_pb.setText("當前進度是+" + pb_num + "%"); break; default: break; } } }; } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } public void downLoad(View v) { DownActivity.flag = true; DownActivity.pb_count = 0; path = et_url.getText().toString(); String threadNum_et = et_num.getText().toString(); if (TextUtils.isEmpty(path) || TextUtils.isEmpty(threadNum_et)) { Toast.makeText(this, "不能為空", Toast.LENGTH_LONG).show(); return; } Toast.makeText(this, "url:" + path + "--" + threadNum_et, Toast.LENGTH_LONG).show(); // 轉換成數字 threadNum = Integer.valueOf(threadNum_et); new Thread(new Runnable() { @Override public void run() { try { // 創建出URL對象 URL url = new URL(path); // 創建出 HttpURLConnection對象 HttpURLConnection httpURLConnection = (HttpURLConnection) url .openConnection(); // 設置 發請求發送的方式 httpURLConnection.setRequestMethod("GET"); // 設置請求是否超時時間 httpURLConnection.setConnectTimeout(5000); // 設置 httpURLConnection .setRequestProperty("User-Agent", " Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)"); // 是否響應成功 if (httpURLConnection.getResponseCode() == 200) { // 獲取文件的大小 size = httpURLConnection.getContentLength(); System.out.println("文件的大小" + size); // 設置進度條的最大值 pb_thread.setMax(size); // 創建文件 //保存到SD卡上 // 首先判斷是否擁有sdcard if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { // 獲取sdCard文件目錄對象 File sdFile = Environment .getExternalStorageDirectory(); // 創建文件對象 File file = new File(sdFile, "youdao.exe"); RandomAccessFile accessFile = new RandomAccessFile( file, "rwd"); // 設置文件的大小 accessFile.setLength(size); // 每個線程下載的大小 blockSize = size / threadNum; // 開三個線程 操作此文件 for (int i = 1; i <= threadNum; i++) { // 1 2 3 // 計算出每個線程開始的位置 int startSize = (i - 1) * blockSize; // 結束位置 int endSize = (i) * blockSize; // 當線程是最后一個線程的時候 if (i == threadNum) { // 判斷文件的大小是否大于計算出來的結束位置 if (size > endSize) { // 結束位置 等于 文件的大小 endSize = size; } } // 為每個線程創建一個隨機的讀取 RandomAccessFile threadAccessFile = new RandomAccessFile( file, "rwd"); new Thread(new DownLoadThread(i, threadAccessFile, startSize, endSize, path)).start(); } } } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }).start(); } /** * 暫停操作 * * @param v */ public void downPause(View v) { Toast.makeText(this, "暫停", Toast.LENGTH_LONG).show(); this.flag = false; }}DownLoadThread.java：
package com.example.downloads.utils;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import com.example.downloads.DownActivity;import android.os.Environment;public class DownLoadThread implements Runnable { public RandomAccessFile accessFile; // 每個線程 都擁有一個accessFile的文件對象 線程1 線程2 線程3 // 線程下載文件的起始位置 public int startSize; public int endSize; // 文件下載的path路徑 public String path; public int threadId; // 線程的標識 public DownLoadThread(int threadId, RandomAccessFile accessFile, int startSize, int endSize, String path) { this.threadId = threadId; this.accessFile = accessFile; this.startSize = startSize; this.endSize = endSize; this.path = path; } @Override public void run() { // 執行run方法 try { // 創建文件到SD卡上去 // 首先判斷是否擁有sdcard if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { // 獲取sdCard文件目錄對象 File sdFile = Environment.getExternalStorageDirectory(); File threadFile = new File(sdFile, threadId + ".txt"); if (threadFile.exists()) { // 讀取該文件的內容 // 創建文件的輸入流對象 FileInputStream fis = new FileInputStream(threadFile); // 采用工具類讀取 byte data[] = StreamTools.isToData(fis); // 轉化成字符串 String threadLen = new String(data); if ((threadLen != null) && (!"".equals(threadLen))) { startSize = Integer.valueOf(threadLen); // 解決 416bug的錯誤 if (startSize > endSize) { startSize = endSize - 1; } } } // 創建文件 // 創建URL對象 URL url = new URL(path); // 創建HttpURLConnection對象 HttpURLConnection httpURLConnection = (HttpURLConnection) url .openConnection(); // 設置請求的頭 httpURLConnection.setRequestMethod("GET"); // 設置請求是否超時時間 httpURLConnection.setConnectTimeout(5000); // 設置 httpURLConnection .setRequestProperty("User-Agent", " Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)"); // 關鍵的設置 httpURLConnection.setRequestProperty("Range", "bytes=" + startSize + "-" + endSize); // 輸出當前線程 System.out.println("當前線程" + threadId + " 下載開始位置:" + startSize + " 下載結束位置:" + endSize); // 響應成功 // 設置隨機讀取文件的 開始位置 accessFile.seek(startSize); // 獲取相應流對象 InputStream is = httpURLConnection.getInputStream(); // 創建輸出流對象 byte buffer[] = new byte[1024]; int len = 0; int threadTotal = 0;// 每個線程下載后保存記錄 / while ((len = is.read(buffer)) != -1) { accessFile.write(buffer, 0, len); threadTotal += len;// 記錄你寫入的長度 //xml文件 //改變進度條： setProgressBar(len); // 通過文件記錄文件下載的長度 FileOutputStream fos = new FileOutputStream(threadFile); fos.write((threadTotal + "").getBytes()); fos.flush(); fos.close(); //發送handler消息 DownActivity.handler.sendEmptyMessage(DownActivity.TEXTVALUE); if(!DownActivity.flag){ return; } } accessFile.close(); is.close(); System.out.println(threadId + "線程執行完畢"); // 線程操作 synchronized (DownActivity.class) { DownActivity.threadCount++; if (DownActivity.threadCount >= DownActivity.threadNum) { for (int i = 1; i <= DownActivity.threadNum; i++) { // 獲取sdCard上的文件 File deleteFile = new File(sdFile, i + ".txt"); if (deleteFile.exists()) { // 文件刪除 deleteFile.delete(); } } } } } } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public synchronized void setProgressBar(int len){ DownActivity.pb_count+=len; DownActivity.pb_thread.setProgress(DownActivity.pb_count); }}StreamTools.java：
package com.example.downloads.utils;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;public class StreamTools { public static byte[] isToData(InputStream is) throws IOException{ // 字節輸出流 ByteArrayOutputStream bops = new ByteArrayOutputStream(); // 讀取數據的緩存區 byte buffer[] = new byte[1024]; // 讀取長度的記錄 int len = 0; // 循環讀取 while ((len = is.read(buffer)) != -1) { bops.write(buffer, 0, len); } // 把讀取的內容轉換成byte數組 byte data[] = bops.toByteArray(); bops.flush(); bops.close(); is.close(); return data; }}strings.xml：
<?xml version="1.0" encoding="utf-8"?><resources> <string name="app_name">downloads</string> <string name="action_settings">Settings</string> <string name="tv_down">文件下載的地址</string> <string name="tv_threadNum">線程數量</string> <string name="tv_num">0%</string> <string name="btn_text">下載</string> <string name="btn_pause">暫停</string> <string name="et_path">http://172.22.64.8:8080/doudou/youdao.exe</string> <string name="et_threadNum">3</string></resources>
布局文件：
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".DownActivity" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:text="@string/tv_down" /> <EditText android:id="@+id/et_path" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/textView1" android:ems="10" android:inputType="none" android:text="@string/et_path" > <requestFocus /> </EditText> <TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_below="@+id/et_path" android:text="@string/tv_threadNum" /> <EditText android:id="@+id/et_threadNum" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/textView2" android:layout_alignRight="@+id/et_path" android:layout_below="@+id/textView2" android:ems="10" android:inputType="number" android:text="@string/et_threadNum" /> <ProgressBar android:id="@+id/pb_down" style="?android:attr/progressBarStyleHorizontal" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/et_threadNum" android:layout_alignRight="@+id/et_threadNum" android:layout_below="@+id/et_threadNum" android:layout_marginTop="14dp" /> <TextView android:id="@+id/tv_pb" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignRight="@+id/textView1" android:layout_below="@+id/pb_down" android:layout_marginTop="24dp" android:text="@string/tv_num" /> <Button android:id="@+id/btn_down" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/pb_down" android:layout_below="@+id/tv_pb" android:layout_marginTop="32dp" android:onClick="downLoad" android:text="@string/btn_text" /> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/btn_down" android:layout_below="@+id/btn_down" android:layout_marginTop="16dp" android:onClick="downPause" android:text="@string/btn_pause" /></RelativeLayout>
效果如下：
最后要注意的是別忘了在項目清單文件中加入權限：
<!-- SDCard權限 --><uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /><!-- 訪問網絡的權限 --><uses-permission android:name="android.permission.INTERNET" />
希望本文所述對大家Android程序設計有所幫助。
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