如何在android中访问外部存储（可移动SD卡）？

Question

我一直在尝试访问内部和外部的SD卡在Android。我已经尝试了很多StackOverFlow中可用的代码，但在大多数或所有Android版本上都不起作用。然后，我找到了两个解决方案。一个在Kitkat &上面工作，另一个在比Kitkat更低的地方工作。我试图合并他们两个，它的工作原理！

如果有人比这更好的解决方案，请分享。

Answer 1

这两个答案是我合并得到它的工作。

1. How to get SD_Card path in android6.0 programmatically

2. Find an external SD card location

这里的解决方案，

加入这行代码在AndroidManifest.xml从Android获得权限读取外部存储器。

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> 

现在，将此类添加到您的项目中。

public class StoragePath { 
File[] getExternalFilesDirs; 

/** 
* Constructor for KitKat & above 
* @param getExternalFilesDirs 
*/ 
public StoragePath(File[] getExternalFilesDirs) { 
    this.getExternalFilesDirs = getExternalFilesDirs; 
} 

/** 
* Constructor for lower than Kitkat 
* 
*/ 
public StoragePath() { 

} 

public String[] getDeviceStorages() { 
    List<String> results = new ArrayList<>(); 

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) { //Method 1 for KitKat & above 
     File[] externalDirs = getExternalFilesDirs; 

     for (File file : externalDirs) { 
      String path = file.getPath().split("/Android")[0]; 

      boolean addPath = false; 

      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { 
       addPath = Environment.isExternalStorageRemovable(file); 
      } else { 
       addPath = Environment.MEDIA_MOUNTED.equals(EnvironmentCompat.getStorageState(file)); 
      } 

      if (addPath) { 
       results.add(path); 
      } 
     } 
    } 

    if (results.isEmpty()) { //Method 2 for all versions 
     final List<String> out = new ArrayList<>(); 
     String reg = "(?i).*vold.*(vfat|ntfs|exfat|fat32|ext3|ext4).*rw.*"; 
     String s = ""; 
     try { 
      final Process process = new ProcessBuilder().command("mount") 
        .redirectErrorStream(true).start(); 
      process.waitFor(); 
      final InputStream is = process.getInputStream(); 
      final byte[] buffer = new byte[1024]; 
      while (is.read(buffer) != -1) { 
       s = s + new String(buffer); 
      } 
      is.close(); 
     } catch (final Exception e) { 
      e.printStackTrace(); 
     } 

     // parse output 
     final String[] lines = s.split("\n"); 
     for (String line : lines) { 
      if (!line.toLowerCase(Locale.US).contains("asec")) { 
       if (line.matches(reg)) { 
        String[] parts = line.split(" "); 
        for (String part : parts) { 
         if (part.startsWith("/")) 
          if (!part.toLowerCase(Locale.US).contains("vold")) 
           out.add(part); 
        } 
       } 
      } 
     } 
     results.addAll(out); 
    } 

    //Below few lines is to remove paths which may not be external memory card, like OTG (feel free to comment them out) 
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
     for (int i = 0; i < results.size(); i++) { 
      if (!results.get(i).toLowerCase().matches(".*[0-9a-f]{4}[-][0-9a-f]{4}")) { 
       Log.d("Tag", results.get(i) + " might not be extSDcard"); 
       results.remove(i--); 
      } 
     } 
    } else { 
     for (int i = 0; i < results.size(); i++) { 
      if (!results.get(i).toLowerCase().contains("ext") && !results.get(i).toLowerCase().contains("sdcard")) { 
       Log.d("Tag", results.get(i) + " might not be extSDcard"); 
       results.remove(i--); 
      } 
     } 
    } 

    //Get path to the Internal Storage aka ExternalStorageDirectory 
    final String internalStoragePath = Environment.getExternalStorageDirectory().getAbsolutePath(); 
    results.add(0, internalStoragePath); 

    String[] storageDirectories = new String[results.size()]; 
    for (int i = 0; i < results.size(); ++i) storageDirectories[i] = results.get(i); 

    return storageDirectories; 

} 
} 

我们使用这个类，

StoragePath storagePath; 
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) { 
     storagePath = new StoragePath(getExternalFilesDirs(null)); 
}else { 
     storagePath = new StoragePath(); 
} 

String[] storages; 
storages = storagePath.getDeviceStorages(); 

String数组storages现在包含了存储器的路径。