Android：下载文件并保存在SD卡上
试图创建一个应用程序来下载SD卡上的文件，这是我的代码：
public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); new Thread(new Runnable() { public void run() { Log.i("step0","it starts here"); URLConnection urlConnection = null; // TODO Auto-generated method stub try { //fetching the URL Log.i("step 1.1","getting the url"); URL url = new URL("http://people.opera.com/howcome/2005/ala/sample.pdf"); Log.i("step 1.2","captured the url"); urlConnection = url.openConnection(); Log.i("step 1.3","captured the url"); urlConnection.connect(); Log.i("step 1","fetching the URL"); //specifying path and file name File sdcard = Environment.getExternalStorageDirectory(); File file = new File(sdcard, "filename.pdf"); Log.i("step 2","specifying path and file name"); //Preparing for download FileOutputStream fileOutput = new FileOutputStream(file); InputStream inputStream = urlConnection.getInputStream(); byte[] buffer = new byte[1024]; int bufferLength = 0; Log.i("step 3","Preparing for download"); //Downloading while ( (bufferLength = inputStream.read(buffer)) > 0 ) { fileOutput.write(buffer, 0, bufferLength); } fileOutput.close(); Log.i("step 4","Downloading"); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }).start(); } @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; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } } 清单文件中的权限：
我的日志文件：
09-11 16:27:27.835: D/jdwp(5892): sendBufferedRequest : len=0x47 09-11 16:27:27.865: W/asset(5892): AssetManager-->addDefaultAssets CIP path not exsit! 09-11 16:27:27.920: V/PhoneWindow(5892): DecorView setVisiblity: visibility = 4 09-11 16:27:27.921: I/step0(5892): it starts here 09-11 16:27:27.922: I/step 1.1(5892): getting the url 09-11 16:27:27.923: I/step 1.2(5892): captured the url 09-11 16:27:27.924: I/step 1.3(5892): captured the url 09-11 16:27:27.935: D/libc-netbsd(5892): getaddrinfo: people.opera.com NO result from proxy 09-11 16:27:27.937: I/System.out(5892): [CDS][DNS]Unable to resolve host "people.opera.com": No address associated with hostname 09-11 16:27:27.937: W/System.err(5892): java.net.UnknownHostException: Unable to resolve host "people.opera.com": No address associated with hostname 09-11 16:27:27.938: W/System.err(5892): at java.net.InetAddress.lookupHostByName(InetAddress.java:439) 09-11 16:27:27.938: W/System.err(5892): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 09-11 16:27:27.938: W/System.err(5892): at java.net.InetAddress.getAllByName(InetAddress.java:214) 09-11 16:27:27.938: W/System.err(5892): at libcore.net.http.HttpConnection.(HttpConnection.java:70) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpConnection.(HttpConnection.java:50) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpEngine.connect(HttpEngine.java:311) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240) 09-11 16:27:27.939: W/System.err(5892): at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:81) 09-11 16:27:27.940: W/System.err(5892): at com.android.installapp.MainActivity$1.run(MainActivity.java:53) 09-11 16:27:27.940: W/System.err(5892): at java.lang.Thread.run(Thread.java:838) 09-11 16:27:27.940: W/System.err(5892): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname) 09-11 16:27:27.941: W/System.err(5892): at libcore.io.Posix.getaddrinfo(Native Method) 09-11 16:27:27.941: W/System.err(5892): at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:59) 09-11 16:27:27.941: W/System.err(5892): at java.net.InetAddress.lookupHostByName(InetAddress.java:405) 09-11 16:27:27.941: W/System.err(5892): ... 14 more 09-11 16:27:27.941: W/System.err(5892): Caused by: libcore.io.ErrnoException: getaddrinfo failed: ENETUNREACH (Network is unreachable) 09-11 16:27:27.942: W/System.err(5892): ... 17 more 09-11 16:27:27.960: V/PhoneWindow(5892): DecorView setVisiblity: visibility = 0 09-11 16:27:28.064: D/libEGL(5892): loaded /system/lib/egl/libEGL_mali.so 09-11 16:27:28.072: D/libEGL(5892): loaded /system/lib/egl/libGLESv1_CM_mali.so 09-11 16:27:28.079: D/libEGL(5892): loaded /system/lib/egl/libGLESv2_mali.so 09-11 16:27:28.183: D/OpenGLRenderer(5892): Enabling debug mode 0 09-11 16:27:28.186: V/InputMethodManager(5892): onWindowFocus: null softInputMode=32 first=true flags=#1810100 09-11 16:27:28.187: V/InputMethodManager(5892): START INPUT: com.android.internal.policy.impl.PhoneWindow$DecorView{413fb9c0 VE.... R.....ID 0,0-480,854} ic=null tba=android.view.inputmethod.EditorInfo@4141e938 controlFlags=#104 09-11 16:27:28.282: V/InputMethodManager(5892): Starting input: Bind result=InputBindResult{null com.android.inputmethod.latin/.LatinIME #47} 09-11 16:27:28.286: V/InputMethodManager(5892): onWindowFocus: null softInputMode=32 first=false flags=#1810100 09-11 16:27:28.290: V/PhoneWindow(5892): DecorView setVisiblity: visibility = 0 09-11 16:27:28.401: W/IInputConnectionWrapper(5892): showStatusIcon on inactive InputConnection
我尝试在互联网上搜索，但我无法解决这个问题。它没有下载文件。 有人可以帮忙吗？
尝试这个：
try { //set the download URL, a url that points to a file on the internet //this is the file to be downloaded URL url = new URL("http://somewhere.com/some/webhosted/file"); //create the new connection HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); //set up some things on the connection urlConnection.setRequestMethod("GET"); urlConnection.setDoOutput(true); //and connect! urlConnection.connect(); //set the path where we want to save the file //in this case, going to save it on the root directory of the //sd card. File SDCardRoot = Environment.getExternalStorageDirectory(); //create a new file, specifying the path, and the filename //which we want to save the file as. File file = new File(SDCardRoot,"somefile.ext"); //this will be used to write the downloaded data into the file we created FileOutputStream fileOutput = new FileOutputStream(file); //this will be used in reading the data from the internet InputStream inputStream = urlConnection.getInputStream(); //this is the total size of the file int totalSize = urlConnection.getContentLength(); //variable to store total downloaded bytes int downloadedSize = 0; //create a buffer... byte[] buffer = new byte[1024]; int bufferLength = 0; //used to store a temporary size of the buffer //now, read through the input buffer and write the contents to the file while ( (bufferLength = inputStream.read(buffer)) > 0 ) { //add the data in the buffer to the file in the file output stream (the file on the sd card fileOutput.write(buffer, 0, bufferLength); //add up the size so we know how much is downloaded downloadedSize += bufferLength; //this is where you would do something to report the prgress, like this maybe updateProgress(downloadedSize, totalSize); } //close the output stream when done fileOutput.close(); //catch some possible errors... } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }
如果您从URL下载文件，请尝试下面带有文件夹名称和文件名的代码
public void DownloadFile(String strUrl, String folderName, String fileName) { try { File dir = new File(Environment.getExternalStorageDirectory() + "/" + folderName); if (dir.exists() == false) { dir.mkdirs(); } URL url = new URL(strUrl); File file = new File(dir, fileName); URLConnection ucon = url.openConnection(); InputStream is = ucon.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); ByteArrayBuffer baf = new ByteArrayBuffer(20000); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } FileOutputStream fos = new FileOutputStream(file); fos.write(baf.toByteArray()); fos.flush(); fos.close(); } catch (IOException e) { e.printStackTrace(); } }