在Activity中或者Service中開啟子執行緒：

private void playvideo() {
		if (!URLUtil.isNetworkUrl(this.remoteUrl)) {
			mVideoView.setVideoPath(this.remoteUrl);
			mVideoView.start();
			return;
		}

		showProgressDialog();  // 顯示進度條

		new Thread(new Runnable() {

			@Override
			public void run() {
				FileOutputStream out = null;
				InputStream is = null;
				try {
					if (localUrl == null) {
						localUrl = Environment.getExternalStorageDirectory()
								.getAbsolutePath()
								+ "/VideoCache/"
								+ System.currentTimeMillis() + ".mp4";   // 建立本地檔案的路徑
					}
					System.out.println("獲取本地SD卡的Url TWO: " + localUrl);
					
					File cacheFile = new File(localUrl);
					if (!cacheFile.exists()) {     // 如果快取檔案不存在，就建立
						cacheFile.getParentFile().mkdirs();
						cacheFile.createNewFile();
					}
					
					readSize = cacheFile.length();
					System.out.println("快取視訊檔案的長度" + readSize);
					out = new FileOutputStream(cacheFile, true);
					
					URL url = new URL(remoteUrl);
					HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();
					httpConnection.setRequestProperty("User-Agent", "NetFox");
					httpConnection.setRequestProperty("RANGE", "bytes=" + readSize + "-");

					is = httpConnection.getInputStream();

					mediaLength = httpConnection.getContentLength();
					if (mediaLength == -1) {
						return;
					}

					mediaLength += readSize;

					byte buf[] = new byte[4 * 1024];
					int size = 0;
					/**最後讀取的大小*/
					long lastReadSize = 0;

					mHandler.sendEmptyMessage(VIDEO_STATE_UPDATE);

					while ((size = is.read(buf)) != -1) {   // 
						try {
							out.write(buf, 0, size);   // 把網路視訊檔案寫入SD卡中
							readSize += size;
						} catch (Exception e) {
							e.printStackTrace();
						}

						if (!isready) {
							if ((readSize - lastReadSize) > READY_BUFF) {
								lastReadSize = readSize;
								mHandler.sendEmptyMessage(CACHE_VIDEO_READY);
							}
						} else {
							if ((readSize - lastReadSize) > CACHE_BUFF * (errorCnt + 1)) {
								lastReadSize = readSize;
								mHandler.sendEmptyMessage(CACHE_VIDEO_UPDATE);
							}
						}
					}

					mHandler.sendEmptyMessage(CACHE_VIDEO_END);
				} catch (Exception e) {
					e.printStackTrace();
				} finally {
					if (out != null) {
						try {
							out.close();
						} catch (IOException e) {
						}
					}

					if (is != null) {
						try {
							is.close();
						} catch (IOException e) {
						}
					}
				}

			}
		}).start();

	}
 

由上面可以看出，要把檔案儲存到SD卡上面，分為下面幾步：

1.首先建立一個目錄或者說是路徑，放到檔案中，判斷檔案是否存在，存在就把網路上面的轉換成流存到SD中，不存在，就在SD卡中建立這樣的目錄。

				       String localUrl = Environment.getExternalStorageDirectory()
								.getAbsolutePath()
								+ "/VideoCache/"
								+ System.currentTimeMillis() + ".mp4";   // 建立本地檔案的路徑
					
					File cacheFile = new File(localUrl);
					if (!cacheFile.exists()) {     // 如果檔案不存在，就建立
						cacheFile.getParentFile().mkdirs();
						cacheFile.createNewFile();
					}
 

FileOutputStream out = new FileOutputStream(cacheFile, true);
					URL url = new URL(remoteUrl); //引數就是網路連結
					HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();
					httpConnection.setRequestProperty("User-Agent", "NetFox");
					httpConnection.setRequestProperty("RANGE", "bytes=" + readSize + "-");
					InputStream is = httpConnection.getInputStream();		// 把網路連線轉換成輸入流
					
byte buf[] = new byte[4 * 1024];
					int size = 0;

					mHandler.sendEmptyMessage(VIDEO_STATE_UPDATE);

					while ((size = is.read(buf)) != -1) {   // 
						try {
							out.write(buf, 0, size);   // 把網路視訊檔案寫入SD卡中
							readSize += size;
						} catch (Exception e) {
							e.printStackTrace();
						}
					}


if (out != null) {
						try {
							out.close();
						} catch (IOException e) {
						}
					}

					if (is != null) {
						try {
							is.close();
						} catch (IOException e) {
						}
					}
 

String localUrl = Environment.getExternalStorageDirectory().getAbsolutePath()
								+ "/VideoCache/"
								+ System.currentTimeMillis() + ".mp4";   // 獲取本地SD卡檔案的路徑

4.SD卡的許可權

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> 
<uses-permission android:name="android.permission.WRITE_MEDIA_STORAGE" />