如何判斷sdcard是否安裝在Android中？

Question

我正在研究一個需要查看用戶存儲的圖像的Android應用程序。問題是，如果用戶通過USB電纜安裝了SD卡，我無法讀取磁盤上的圖像列表。

有誰知道一種方法來告訴如果安裝了USB，以便我可以彈出一條消息，通知用戶它將無法工作？

Answer 1

如果你想訪問設備上的圖像，最好的方法是使用MediaStore content provider。訪問它作爲content provider將允許您查詢存在的圖像，並在適當的情況下將content:// URL映射到設備上的文件路徑。

如果您仍需要訪問SD卡，相機應用程序包括ImageUtils類，如果SD卡安裝進行如下的檢查：

static public boolean hasStorage(boolean requireWriteAccess) { 
    //TODO: After fix the bug, add "if (VERBOSE)" before logging errors. 
    String state = Environment.getExternalStorageState(); 
    Log.v(TAG, "storage state is " + state); 

    if (Environment.MEDIA_MOUNTED.equals(state)) { 
     if (requireWriteAccess) { 
      boolean writable = checkFsWritable(); 
      Log.v(TAG, "storage writable is " + writable); 
      return writable; 
     } else { 
      return true; 
     } 
    } else if (!requireWriteAccess && Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
     return true; 
    } 
    return false; 
} 

Answer 2

我很抱歉發佈非Android方法來做到這一點，希望有人可以使用Android API提供答案。

您可以列出sdcard根目錄下的文件。如果沒有，則SD卡要麼完全空白（不尋常，但可能）或未安裝。如果你嘗試在SD卡上創建一個空文件並且失敗，這意味着你試圖在SD卡的掛載點上創建一個文件，由於權限問題而被拒絕，所以你會知道sdcard不是安裝。

是的，我知道這是醜陋....

Answer 3

public static boolean isSdPresent() { 

return android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED); 

} 

Answer 4

這裏是jargonjustin的checkFsWritable缺少的功能後

private static boolean checkFsWritable() { 
     // Create a temporary file to see whether a volume is really writeable. 
     // It's important not to put it in the root directory which may have a 
     // limit on the number of files. 
     String directoryName = Environment.getExternalStorageDirectory().toString() + "/DCIM"; 
     File directory = new File(directoryName); 
     if (!directory.isDirectory()) { 
      if (!directory.mkdirs()) { 
       return false; 
      } 
     } 
     return directory.canWrite(); 
    } 

Answer 5

我用光標從SD卡上檢索圖像，當沒有SD卡插入設備遊標爲空。 事實上，當通過從設備上物理移除卡來卸載SD卡時，就是這種情況。這是我所使用的代碼：

Cursor mCursor = this.getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null, null, null, null); 
    if (mCursor == null || !mCursor .moveToFirst()) { 
       /** 
       *mCursor == null: 
       * - query failed; the app don't have access to sdCard; example: no sdCard 
       * 
       *!mCursor.moveToFirst(): 
       *  - there is no media on the device 
       */ 
      } else { 
       // process the images... 
       mCursor.close(); 
    } 

更多信息：http://developer.android.com/guide/topics/media/mediaplayer.html#viacontentresolver

Answer 6

在jargonjustin的帖子：

文件ImageManager.java

方法hasStorage - >

public static boolean hasStorage(boolean requireWriteAccess) { 
     String state = Environment.getExternalStorageState(); 

     if (Environment.MEDIA_MOUNTED.equals(state)) { 
      if (requireWriteAccess) { 
       boolean writable = checkFsWritable(); 
       return writable; 
      } else { 
       return true; 
      } 
     } else if (!requireWriteAccess 
       && Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
      return true; 
     } 
     return false; 
    } 

方法checkFsWritable - >

private static boolean checkFsWritable() { 
     // Create a temporary file to see whether a volume is really writeable. 
     // It's important not to put it in the root directory which may have a 
     // limit on the number of files. 
     String directoryName = 
       Environment.getExternalStorageDirectory().toString() + "/DCIM"; 
     File directory = new File(directoryName); 
     if (!directory.isDirectory()) { 
      if (!directory.mkdirs()) { 
       return false; 
      } 
     } 
     File f = new File(directoryName, ".probe"); 
     try { 
      // Remove stale file if any 
      if (f.exists()) { 
       f.delete(); 
      } 
      if (!f.createNewFile()) { 
       return false; 
      } 
      f.delete(); 
      return true; 
     } catch (IOException ex) { 
      return false; 
     } 
    } 

Answer 7

Cool....Check it out... 
try { 
      File mountFile = new File("/proc/mounts"); 
      usbFoundCount=0; 
      sdcardFoundCount=0; 
      if(mountFile.exists()) 
      { 
       Scanner usbscanner = new Scanner(mountFile); 
       while (usbscanner.hasNext()) { 
        String line = usbscanner.nextLine(); 
        if (line.startsWith("/dev/fuse /storage/usbcard1")) { 
         usbFoundCount=1; 
         Log.i("-----USB--------","USB Connected and properly mounted---/dev/fuse /storage/usbcard1"); 
        } 
      } 
     } 
      if(mountFile.exists()){ 
       Scanner sdcardscanner = new Scanner(mountFile); 
       while (sdcardscanner.hasNext()) { 
        String line = sdcardscanner.nextLine(); 
        if (line.startsWith("/dev/fuse /storage/sdcard1")) { 
         sdcardFoundCount=1; 
         Log.i("-----USB--------","USB Connected and properly mounted---/dev/fuse /storage/sdcard1"); 
        } 
      } 
     } 
      if(usbFoundCount==1) 
      { 
       Toast.makeText(context,"USB Connected and properly mounted", 7000).show(); 
       Log.i("-----USB--------","USB Connected and properly mounted"); 
      } 
      else 
      { 
       Toast.makeText(context,"USB not found!!!!", 7000).show(); 
       Log.i("-----USB--------","USB not found!!!!"); 

      } 
      if(sdcardFoundCount==1) 
      { 
       Toast.makeText(context,"SDCard Connected and properly mounted", 7000).show(); 
       Log.i("-----SDCard--------","SDCard Connected and properly mounted"); 
      } 
      else 
      { 
       Toast.makeText(context,"SDCard not found!!!!", 7000).show(); 
       Log.i("-----SDCard--------","SDCard not found!!!!"); 

      } 
     }catch (Exception e) { 
      e.printStackTrace(); 
     } 

Answer 8

在你做與外部存儲的任何工作，你應該總是調用getExternalStorageState（）檢查介質是否可用。媒體可能被掛載到計算機，缺失，只讀或其他狀態。例如，這裏是你可以用它來檢查可用性一對夫婦的方法：

/* Checks if external storage is available for read and write */ 
public boolean isExternalStorageWritable() { 
    String state = Environment.getExternalStorageState(); 
    if (Environment.MEDIA_MOUNTED.equals(state)) { 
     return true; 
    } 
    return false; 
} 

/* Checks if external storage is available to at least read */ 
public boolean isExternalStorageReadable() { 
    String state = Environment.getExternalStorageState(); 
    if (Environment.MEDIA_MOUNTED.equals(state) || 
     Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
     return true; 
    } 
    return false; 
} 

來源： http://developer.android.com/guide/topics/data/data-storage.html