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這篇文章主要介紹了Android如何實現簡單斷點續傳和下載到本地功能,具有一定借鑒價值,感興趣的朋友可以參考下,希望大家閱讀完這篇文章之后大有收獲,下面讓小編帶著大家一起了解一下。
具體內容如下
效果展示
導入依賴與權限
依賴
compile 'com.loopj.android:android-async-http:1.4.9'
權限
<uses-permission android:name="android.permission.INTERNET"></uses-permission> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
主MainActivity(布局)
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" 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="com.lv.mama.test004.MainActivity"> <ProgressBar android:layout_width="match_parent" android:layout_height="20dp" android:layout_marginTop="15dp" android:id="@+id/pb" android:layout_alignParentTop="true" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" /> <TextView android:text="TextView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/pb" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:layout_marginLeft="20dp" android:layout_marginStart="20dp" android:layout_marginTop="13dp" android:id="@+id/tv_info" /> <Button android:text="暫停" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="17dp" android:id="@+id/bt_pause" android:onClick="pause" android:layout_below="@+id/tv_info" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:layout_marginLeft="11dp" android:layout_marginStart="11dp" /> <Button android:text="開始" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginRight="24dp" android:layout_marginEnd="24dp" android:id="@+id/bt_download" android:onClick="download" android:layout_alignBaseline="@+id/bt_pause" android:layout_alignBottom="@+id/bt_pause" android:layout_alignParentRight="true" android:layout_alignParentEnd="true" /> </RelativeLayout>
主MainActivity
public class MainActivity extends AppCompatActivity { protected static final String TAG = "OtherActivity"; //下載線程的數量 private final static int threadsize = 3; protected static final int SET_MAX = 0; public static final int UPDATE_VIEW = 1; private ProgressBar pb; private Button bt_download; private Button bt_pause; private TextView tv_info; //顯示進度和更新進度 private Handler mHandler = new Handler() { public void handleMessage(android.os.Message msg) { switch (msg.what) { case SET_MAX://設置進度條的最大值 int filelength = msg.arg1; pb.setMax(filelength); break; case UPDATE_VIEW://更新進度條 和 下載的比率 int len = msg.arg1;//新下載的長度 pb.setProgress(pb.getProgress() + len);//設置進度條的刻度 int max = pb.getMax();//獲取進度的最大值 int progress = pb.getProgress();//獲取已經下載的數據量 // 下載:30 總:100 int result = (progress * 100) / max; tv_info.setText("下載:" + result + "%"); break; default: break; } } ; }; String uri = "http://c.hiphotos.baidu.com/image/pic/item/b90e7bec54e736d1e51217c292504fc2d46269f3.jpg"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //找到控件 pb = (ProgressBar) findViewById(R.id.pb); tv_info = (TextView) findViewById(R.id.tv_info); bt_download = (Button) findViewById(R.id.bt_download); bt_pause = (Button) findViewById(R.id.bt_pause); //數據的回顯 //確定下載的文件 String name = getFileName(uri); File file = new File(Environment.getExternalStorageDirectory(), name); if (file.exists()) {//文件存在回顯 //獲取文件的大小 int filelength = (int) file.length(); pb.setMax(filelength); try { //統計原來所有的下載量 int count = 0; //讀取下載記錄文件 for (int threadid = 0; threadid < threadsize; threadid++) { //獲取原來指定線程的下載記錄 int existDownloadLength = readDownloadInfo(threadid); count = count + existDownloadLength; } //設置進度條的刻度 pb.setProgress(count); //計算比率 int result = (count * 100) / filelength; tv_info.setText("下載:" + result + "%"); } catch (Exception e) { e.printStackTrace(); } } } //暫停 private boolean flag = false;//是否在下載 public void pause(View v){ flag = false; bt_download.setEnabled(true); bt_pause.setEnabled(false); } //下載 public void download(View v){ flag = true; //是在下載 bt_download.setEnabled(false);//一點擊變成不可點擊 bt_pause.setEnabled(true);//一點擊變成可點擊 new Thread(){//子線程 public void run() { try { //獲取服務器上文件的大小 HttpClient client = new DefaultHttpClient(); HttpHead request = new HttpHead(uri); HttpResponse response = client.execute(request); //response 只有響應頭 沒有響應體 if(response.getStatusLine().getStatusCode() == 200){ Header[] headers = response.getHeaders("Content-Length"); String value = headers[0].getValue(); //文件大小 int filelength = Integer.parseInt(value); Log.i(TAG, "filelength:"+filelength); //設置進度條的最大值 Message msg_setmax = Message.obtain(mHandler, SET_MAX, filelength, 0); msg_setmax.sendToTarget(); //處理下載記錄文件 for(int threadid=0;threadid<threadsize;threadid++){ //對應的下載記錄文件 File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt"); //判斷文件是否存在 if(!file.exists()){ //創建文件 file.createNewFile(); } } //在sdcard創建和服務器大小一樣的文件 String name = getFileName(uri); File file = new File(Environment.getExternalStorageDirectory(),name); //隨機訪問文件 RandomAccessFile raf = new RandomAccessFile(file, "rwd"); //設置文件的大小 raf.setLength(filelength); //關閉 raf.close(); //計算每條線程的下載量 int block = (filelength%threadsize == 0)?(filelength/threadsize):(filelength/threadsize+1); //開啟三條線程執行下載 for(int threadid=0;threadid<threadsize;threadid++){ new DownloadThread(threadid, uri, file, block).start(); } } } catch (Exception e) { e.printStackTrace(); } }; }.start(); } //線程下載類 private class DownloadThread extends Thread { private int threadid;//線程的id private String uri;//下載的地址 private File file;//下載文件 private int block;//下載的塊 private int start; private int end; public DownloadThread(int threadid, String uri, File file, int block) { super(); this.threadid = threadid; this.uri = uri; this.file = file; this.block = block; //計算下載的開始位置和結束位置 start = threadid * block; end = (threadid + 1) * block - 1; try { //讀取該條線程原來的下載記錄 int existDownloadLength = readDownloadInfo(threadid); //修改下載的開始位置 從新下載 start = start + existDownloadLength; } catch (Exception e) { e.printStackTrace(); } } //下載 狀態碼:200是普通的下載 206是分段下載 Range:范圍 @Override public void run() { super.run(); try { RandomAccessFile raf = new RandomAccessFile(file, "rwd"); //跳轉到起始位置 raf.seek(start); //分段下載 HttpClient client = new DefaultHttpClient(); HttpGet request = new HttpGet(uri); request.addHeader("Range", "bytes:"+start+"-"+end);//添加請求頭 HttpResponse response = client.execute(request); if(response.getStatusLine().getStatusCode() == 200){ InputStream inputStream = response.getEntity().getContent(); //把流寫入到文件 byte[] buffer = new byte[1024]; int len = 0; while((len = inputStream.read(buffer)) != -1){ //如果暫停下載 點擊暫停 false 就直接return 點擊下載true接著下載 if(!flag){ return;//標準線程結束 } //寫數據 raf.write(buffer, 0, len); //讀取原來下載的數據量 這里讀取是為了更新下載記錄 int existDownloadLength = readDownloadInfo(threadid);//原來下載的數據量 //計算最新的下載 int newDownloadLength = existDownloadLength + len; //更新下載記錄 從新記錄最新下載位置 updateDownloadInfo(threadid, newDownloadLength); //更新進度條的顯示 下載的百分比 Message update_msg = Message.obtain(mHandler, UPDATE_VIEW, len, 0); update_msg.sendToTarget(); //模擬 看到進度條動的效果 SystemClock.sleep(50); } inputStream.close(); raf.close(); Log.i(TAG, "第"+threadid+"條線程下載完成"); } } catch (Exception e) { e.printStackTrace(); } } } /** * 讀取指定線程的下載數據量 * @param threadid 線程的id * @return * @throws Exception */ public int readDownloadInfo(int threadid) throws Exception{ //下載記錄文件 File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt"); BufferedReader br = new BufferedReader(new FileReader(file)); //讀取一行數據 String content = br.readLine(); int downlength = 0; //如果該文件第一次創建去執行讀取操作 文件里面的內容是 null if(!TextUtils.isEmpty(content)){ downlength = Integer.parseInt(content); } //關閉流 br.close(); return downlength; } /** * 更新下載記錄 * @param threadid * @param newDownloadLength */ public void updateDownloadInfo(int threadid,int newDownloadLength) throws Exception{ //下載記錄文件 File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt"); FileWriter fw = new FileWriter(file); fw.write(newDownloadLength+""); fw.close(); } /** * 獲取文件的名稱 * @param uri * @return */ private String getFileName(String uri){ return uri.substring(uri.lastIndexOf("/")+1); } }
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