Android多執行緒斷點續傳下載實現程式碼
阿新 • • 發佈:2020-11-21
學習了多執行緒下載,而且可以斷點續傳的邏輯,執行緒數量可以自己選擇,但是執行緒數量過多手機就承受不起,導致閃退,好在有斷點續傳。
步驟寫在了程式碼的註釋裡。大概就是獲取伺服器檔案的大小,在本地新建一個相同大小的檔案用來申請空間,然後將伺服器的檔案讀下來寫到申請的檔案中去。若開多執行緒,將檔案分塊,計算每個執行緒下載的開始位置和結束位置。若斷點傳輸,則儲存斷開後下載的位置,下次將此位置賦給開始下載的位置即可。細節見程式碼。
下面是效果圖:
佈局檔案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:id="@+id/et_path" 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:id="@+id/et_threadCount" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="請輸入執行緒數量" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="click" android:text="下載" /> <LinearLayout android:id="@+id/ll_pb" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#455eee" android:orientation="vertical"> </LinearLayout> </LinearLayout> </android.support.constraint.ConstraintLayout>
建立佈局檔案,用來動態顯示每個執行緒的進度條
layout.xml:
<?xml version="1.0" encoding="utf-8"?> <ProgressBar xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/progressBar" style="?android:attr/progressBarStyleHorizontal" 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;// 代表正在執行的執行緒 private int threadCount; private List<ProgressBar> pbList;//集合儲存進度條的引用 @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); //新增一個進度條的引用 pbList = new ArrayList<ProgressBar>(); } //點選按鈕實現下載邏輯 public void click(View view) { //獲取下載路徑 path = et_path.getText().toString().trim(); //獲取執行緒數量 String threadCounts = et_threadCount.getText().toString().trim(); //移除以前的進度條新增新的進度條 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新增到幾何中 pbList.add(v); //動態獲取進度條 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(); // 把執行執行緒的數量賦值給runningThread runningThread = threadCount; System.out.println("length=" + length); // 建立一個和伺服器的檔案一樣大小的檔案,提前申請空間 RandomAccessFile randomAccessFile = new RandomAccessFile(getFileName(path),"rw"); randomAccessFile.setLength(length); // 算出每個執行緒下載的大小 int blockSize = length / threadCount; // 計算每個執行緒下載的開始位置和結束位置 for (int i = 0; i < length; i++) { int startIndex = i * blockSize;// 開始位置 int endIndex = (i + 1) * blockSize;// 結束位置 // 特殊情況就是最後一個執行緒 if (i == threadCount - 1) { // 說明是最後一個執行緒 endIndex = length - 1; } // 開啟執行緒去伺服器下載 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 { // 通過構造方法吧每個執行緒的開始位置和結束位置傳進來 private int startIndex; private int endIndex; private int threadID; private int PbMaxSize;//代表當前下載(進度條)的最大值 private int pblastPosition;//如果中斷過,這是進度條上次的位置 public DownLoadThread(int startIndex,int endIndex,int threadID) { this.startIndex = startIndex; this.endIndex = endIndex; this.threadID = threadID; } @Override public void run() { // 實現去伺服器下載檔案 try { //計算進度條最大值 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下載,聰慧檔案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); //賦值給進度條位置 pblastPosition = lastPosition1 - startIndex; // 改變一下startIndex的值 startIndex = lastPosition1 + 1; System.out.println("執行緒id:" + threadID + "真實下載的位置:" + lastPosition + "-------" + endIndex); bufr.close(); fis.close(); } conn.setRequestProperty("Range","bytes=" + startIndex + "-" + endIndex); int code = conn.getResponseCode(); if (code == 206) { // 隨機讀寫檔案物件 RandomAccessFile raf = new RandomAccessFile(getFileName(path),"rw"); // 每個執行緒從自己的位置開始寫 raf.seek(startIndex); InputStream in = conn.getInputStream(); // 把資料寫到檔案中 int len = -1; byte[] buffer = new byte[1024]; int totle = 0;// 代表當前執行緒下載的大小 while ((len = in.read(buffer)) != -1) { raf.write(buffer,len); totle += len; // 實現斷點續傳就是把當前執行緒下載的位置儲存起來,下次再下載的時候按照上次下載的位置繼續下載 int currentThreadPosition = startIndex + totle;// 存到一個txt文字中 // 用來儲存當前執行緒當前下載的位置 RandomAccessFile raff = new RandomAccessFile(getFileName(path) + threadID + ".txt","rwd"); raff.write(String.valueOf(currentThreadPosition).getBytes()); raff.close(); //設定進度條當前的進度 pbList.get(threadID).setMax(PbMaxSize); pbList.get(threadID).setProgress(pblastPosition + totle); } raf.close(); System.out.println("執行緒ID:" + threadID + "下載完成"); // 將產生的txt檔案刪除,每個執行緒下載完成的具體時間不知道 synchronized (DownLoadThread.class) { runningThread--; if (runningThread == 0) { //說明執行緒執行完畢 for (int i = 0; i < threadCount; i++) { File filedel = new File(getFileName(path) + i + ".txt"); filedel.delete(); } } } } } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.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; } }
在清單檔案中新增以下許可權
<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容,希望對大家的學習有所幫助,也希望大家多多支援我們。