直接上代码，需要申请权限：

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

    public void getpic() {
       new Thread(new Runnable() {
           @Override
           public void run() {
               Log.i(TAG, "-->getpic");


//设定查询目录，查询指定目录里面的图片
// String path=  Environment.getExternalStorageDirectory()+ "/Pictures/test";

             // String path = Environment.getExternalStorageDirectory().getAbsolutePath() +
                  //     "/Pictures/Screenshots";
               String path = "/storage/emulated/0/Pictures/test";
               Log.i(TAG, "-->" + path);
//selection: 指定查询条件
               String selection = MediaStore.Images.Media.DATA + " like ?";
//设定查询目录,
//定义selectionArgs：
               String[] selectionArgs = {path + "%"};
// Cursor mCursor = mContext.getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null,
//// selection, selectionArgs, null);
//查看指定文件夹里面的所有文件
               Cursor mCursor = getContentResolver().query(MediaStore.Files.getContentUri("external"), null,
                       selection, selectionArgs, null);
               if (mCursor != null) {
                   while (mCursor.moveToNext()) {
                       // Log.i(TAG, "-->moveToNext");
                       String displayName = mCursor.getString(mCursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME));
                       Log.i(TAG, "-->" + displayName);
                   }
               } else {
                   Log.i(TAG, "-->mCursor is null");
               }
           }
       }).start();


   }

自己创建了test文件夹，里面放了两张图片
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