Android 中 Environment.getExternalStorageDirectory()无效

　　我们在处理缓存的时候，并不是每次都会在应用私有存储空间那里保存，很多时候是需要用到ExternalStorage。我们平时一般都是用Environment.getExternalStorageDirectory()，这在6.0以前一直是好的，（即使不对，那你的问题应该是没注意加权限，或者是格式不对之类又或者sdcard被移走了等等）。但是到了6.0以后，就发现怎么都不无法创建文件了。很多人就疑惑，该加的权限都加了，怎么就没法创建呢？

　　原因是Android 6.0以后，google升级了Android的权限管理机制，对于一些敏感的权限，需要显性申请并被用户允许才可能运行。

 

    private void checkPermission() { if (Build.VERSION.SDK_INT >= 23) { int write = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE); int read = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE); if (write != PackageManager.PERMISSION_GRANTED || read != PackageManager.PERMISSION_GRANTED) { requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE}, 300); } else { String name = "CrashDirectory"; File file1 = new File(Environment.getExternalStorageDirectory(), name); if (file1.mkdirs()) { Log.i("wytings", "permission -------------> " + file1.getAbsolutePath()); } else { Log.i("wytings", "permission -------------fail to make file "); } } } else { Log.i("wytings", "------------- Build.VERSION.SDK_INT < 23 ------------"); } } @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { if (requestCode == 300) { Log.i("wytings", "--------------requestCode == 300->" + requestCode + "," + permissions.length + "," + grantResults.length); } else { Log.i("wytings", "--------------requestCode != 300->" + requestCode + "," + permissions + "," + grantResults); } }

 

备注：附上android的权限组，因为同一组的任何一个权限被授权了，其他权限也自动被授权。例如，一旦WRITE_EXTERNAL_STORAGE被授权了，app也有READ_EXTERNAL_STORAGE.所以，你只申请一个就可以了。

android.permission-group.CALENDAR	android.permission.READ_CALENDAR android.permission.WRITE_CALENDAR
android.permission-group.CAMERA	android.permission.CAMERA
android.permission-group.CONTACTS	android.permission.READ_CONTACTS android.permission.WRITE_CONTACTS android.permission.GET_ACCOUNTS
android.permission-group.LOCATION	android.permission.ACCESS_FINE_LOCATION android.permission.ACCESS_COARSE_LOCATION
android.permission-group.MICROPHONE	android.permission.RECORD_AUDIO
android.permission-group.PHONE	android.permission.READ_PHONE_STATE android.permission.CALL_PHONE android.permission.READ_CALL_LOG android.permission.WRITE_CALL_LOG com.android.voicemail.permission.ADD_VOICEMAIL android.permission.USE_SIP android.permission.PROCESS_OUTGOING_CALLS
android.permission-group.SENSORS	android.permission.BODY_SENSORS
android.permission-group.SMS	android.permission.SEND_SMS android.permission.RECEIVE_SMS android.permission.READ_SMS android.permission.RECEIVE_WAP_PUSH android.permission.RECEIVE_MMS android.permission.READ_CELL_BROADCASTS
android.permission-group.STORAGE	android.permission.READ_EXTERNAL_STORAGE android.permission.WRITE_EXTERNAL_STORAGE