學(xué)習(xí)了多線程下載，而且可以斷點(diǎn)續(xù)傳的邏輯，線程數(shù)量可以自己選擇，但是線程數(shù)量過多手機(jī)就承受不起，導(dǎo)致閃退，好在有斷點(diǎn)續(xù)傳。

步驟寫在了代碼的注釋里。大概就是獲取服務(wù)器文件的大小，在本地新建一個相同大小的文件用來申請空間，然后將服務(wù)器的文件讀下來寫到申請的文件中去。若開多線程，將文件分塊，計(jì)算每個線程下載的開始位置和結(jié)束位置。若斷點(diǎn)傳輸，則保存斷開后下載的位置，下次將此位置賦給開始下載的位置即可。細(xì)節(jié)見代碼。

下面是效果圖：

布局文件activity_main.xml:

<?xml version='1.0' encoding='utf-8'?><android.support.constraint.ConstraintLayout 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' tools:context='.MainActivity'> <LinearLayout android:layout_width='match_parent' android:layout_height='match_parent' android:orientation='vertical'> <EditText android: android:layout_width='match_parent' android:layout_height='wrap_content' android:hint='請輸入下載路徑' android:text='http://10.173.29.234/test.exe' /> <EditText android: android:layout_width='match_parent' android:layout_height='wrap_content' android:hint='請輸入線程數(shù)量' /> <Button android:layout_width='wrap_content' android:layout_height='wrap_content' android:onClick='click' android:text='下載' /> <LinearLayout android: android:layout_width='match_parent' android:layout_height='match_parent' android:background='#455eee' android:orientation='vertical'> </LinearLayout> </LinearLayout></android.support.constraint.ConstraintLayout>

創(chuàng)建布局文件，用來動態(tài)顯示每個線程的進(jìn)度條

layout.xml:

<?xml version='1.0' encoding='utf-8'?><ProgressBar xmlns:android='http://schemas.android.com/apk/res/android' android: android:layout_width='match_parent' android:layout_height='wrap_content' />

MainActivity.java:

import...;public class MainActivity extends AppCompatActivity { private EditText et_path; private EditText et_threadCount; private LinearLayout ll_pb; private String path; private static int runningThread;// 代表正在運(yùn)行的線程 private int threadCount; private List<ProgressBar> pbList;//集合存儲進(jìn)度條的引用 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); et_path = findViewById(R.id.et_path); et_threadCount = findViewById(R.id.et_threadCount); ll_pb = findViewById(R.id.ll_pb); //添加一個進(jìn)度條的引用 pbList = new ArrayList<ProgressBar>(); } //點(diǎn)擊按鈕實(shí)現(xiàn)下載邏輯 public void click(View view) { //獲取下載路徑 path = et_path.getText().toString().trim(); //獲取線程數(shù)量 String threadCounts = et_threadCount.getText().toString().trim(); //移除以前的進(jìn)度條添加新的進(jìn)度條 ll_pb.removeAllViews(); threadCount = Integer.parseInt(threadCounts); pbList.clear(); for (int i = 0; i < threadCount; i++) { ProgressBar v = (ProgressBar) View.inflate(getApplicationContext(), R.layout.layout, null); //把v添加到幾何中 pbList.add(v); //動態(tài)獲取進(jìn)度條 ll_pb.addView(v); } //java邏輯移植 new Thread() { @Override public void run() {/*************/System.out.println('你好');try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod('GET'); conn.setConnectTimeout(5000); int code = conn.getResponseCode(); if (code == 200) { int length = conn.getContentLength(); // 把運(yùn)行線程的數(shù)量賦值給runningThread runningThread = threadCount; System.out.println('length=' + length); // 創(chuàng)建一個和服務(wù)器的文件一樣大小的文件，提前申請空間 RandomAccessFile randomAccessFile = new RandomAccessFile(getFileName(path), 'rw'); randomAccessFile.setLength(length); // 算出每個線程下載的大小 int blockSize = length / threadCount; // 計(jì)算每個線程下載的開始位置和結(jié)束位置 for (int i = 0; i < length; i++) { int startIndex = i * blockSize;// 開始位置 int endIndex = (i + 1) * blockSize;// 結(jié)束位置 // 特殊情況就是最后一個線程 if (i == threadCount - 1) {// 說明是最后一個線程endIndex = length - 1; } // 開啟線程去服務(wù)器下載 DownLoadThread downLoadThread = new DownLoadThread(startIndex, endIndex, i); downLoadThread.start(); } }} catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace();} catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace();}/*************/ } }.start(); } private class DownLoadThread extends Thread { // 通過構(gòu)造方法吧每個線程的開始位置和結(jié)束位置傳進(jìn)來 private int startIndex; private int endIndex; private int threadID; private int PbMaxSize;//代表當(dāng)前下載（進(jìn)度條）的最大值 private int pblastPosition;//如果中斷過，這是進(jìn)度條上次的位置 public DownLoadThread(int startIndex, int endIndex, int threadID) { this.startIndex = startIndex; this.endIndex = endIndex; this.threadID = threadID; } @Override public void run() { // 實(shí)現(xiàn)去服務(wù)器下載文件 try {//計(jì)算進(jìn)度條最大值PbMaxSize = endIndex - startIndex;URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod('GET');conn.setConnectTimeout(5000);// 如果中間斷過，接著上次的位置繼續(xù)下載，聰慧文件中讀取上次下載的位置File file = new File(getFileName(path) + threadID + '.txt');if (file.exists() && file.length() > 0) { FileInputStream fis = new FileInputStream(file); BufferedReader bufr = new BufferedReader(new InputStreamReader(fis)); String lastPosition = bufr.readLine(); int lastPosition1 = Integer.parseInt(lastPosition); //賦值給進(jìn)度條位置 pblastPosition = lastPosition1 - startIndex; // 改變一下startIndex的值 startIndex = lastPosition1 + 1; System.out.println('線程id：' + threadID + '真實(shí)下載的位置：' + lastPosition + '-------' + endIndex); bufr.close(); fis.close();}conn.setRequestProperty('Range', 'bytes=' + startIndex + '-' + endIndex);int code = conn.getResponseCode();if (code == 206) { // 隨機(jī)讀寫文件對象 RandomAccessFile raf = new RandomAccessFile(getFileName(path), 'rw'); // 每個線程從自己的位置開始寫 raf.seek(startIndex); InputStream in = conn.getInputStream(); // 把數(shù)據(jù)寫到文件中 int len = -1; byte[] buffer = new byte[1024]; int totle = 0;// 代表當(dāng)前線程下載的大小 while ((len = in.read(buffer)) != -1) { raf.write(buffer, 0, len); totle += len; // 實(shí)現(xiàn)斷點(diǎn)續(xù)傳就是把當(dāng)前線程下載的位置保存起來，下次再下載的時候按照上次下載的位置繼續(xù)下載 int currentThreadPosition = startIndex + totle;// 存到一個txt文本中 // 用來存儲當(dāng)前線程當(dāng)前下載的位置 RandomAccessFile raff = new RandomAccessFile(getFileName(path) + threadID + '.txt', 'rwd'); raff.write(String.valueOf(currentThreadPosition).getBytes()); raff.close(); //設(shè)置進(jìn)度條當(dāng)前的進(jìn)度 pbList.get(threadID).setMax(PbMaxSize); pbList.get(threadID).setProgress(pblastPosition + totle); } raf.close(); System.out.println('線程ID:' + threadID + '下載完成'); // 將產(chǎn)生的txt文件刪除，每個線程下載完成的具體時間不知道 synchronized (DownLoadThread.class) { runningThread--; if (runningThread == 0) { //說明線程執(zhí)行完畢 for (int i = 0; i < threadCount; i++) {File filedel = new File(getFileName(path) + i + '.txt');filedel.delete(); } } }} } catch (MalformedURLException e) {// TODO Auto-generated catch blocke.printStackTrace(); } catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace(); } } } public String getFileName(String path) { int start = path.lastIndexOf('/') + 1; String subString = path.substring(start); String fileName = '/data/data/com.lgqrlchinese.heima76android_11_mutildownload/' + subString; return fileName; }}

在清單文件中添加以下權(quán)限

<uses-permission android:name='android.permission.INTERNET'/> <uses-permission android:name='android.permission.WRITE_EXTERNAL_STORAGE'/>

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持好吧啦網(wǎng)。