根据文档:

如果此抽象路径名不表示目录，则此方法返回null。

所以你应该检查listFiles是否为空，如果不是则继续

boolean deleteDirectory(File path) {
    if(path.exists()) {
        File[] files = path.listFiles();
        if (files == null) {
            return false;
        }
        for (File file : files) {
            if (file.isDirectory()) {
                deleteDirectory(file);
            } else {
                boolean wasSuccessful = file.delete();
                if (wasSuccessful) {
                    Log.i("Deleted ", "successfully");
                }
            }
        }
    }
    return(path.delete());
}

如果你不需要递归删除东西，你可以尝试这样做:

File file = new File(context.getExternalFilesDir(null), "");
    if (file != null && file.isDirectory()) {
        File[] files = file.listFiles();
        if(files != null) {
            for(File f : files) {   
                f.delete();
            }
        }
    }

这就是我的工作…(简洁且经过测试)

    ...
    deleteDir(new File(dir_to_be_deleted));
    ...

    // delete directory and contents
    void deleteDir(File file) { 
        if (file.isDirectory())
            for (String child : file.list())
                deleteDir(new File(file, child));
        file.delete();  // delete child file or empty directory
    }

根据文档:

如果此抽象路径名不表示目录，则此方法返回null。

所以你应该检查listFiles是否为空，如果不是则继续

boolean deleteDirectory(File path) {
    if(path.exists()) {
        File[] files = path.listFiles();
        if (files == null) {
            return false;
        }
        for (File file : files) {
            if (file.isDirectory()) {
                deleteDirectory(file);
            } else {
                boolean wasSuccessful = file.delete();
                if (wasSuccessful) {
                    Log.i("Deleted ", "successfully");
                }
            }
        }
    }
    return(path.delete());
}

看到android.os。FileUtils，它隐藏在API 21上

public static boolean deleteContents(File dir) {
    File[] files = dir.listFiles();
    boolean success = true;
    if (files != null) {
        for (File file : files) {
            if (file.isDirectory()) {
                success &= deleteContents(file);
            }
            if (!file.delete()) {
                Log.w("Failed to delete " + file);
                success = false;
            }
        }
    }
    return success;
}

来源:https://android.googlesource.com/platform/frameworks/base/ + /主/核心/ java / android / os / FileUtils.java # 414

我把这一个虽然它的步伐，它删除文件夹与任何目录结构。

public int removeDirectory(final File folder) {

    if(folder.isDirectory() == true) {
        File[] folderContents = folder.listFiles();
        int deletedFiles = 0;

        if(folderContents.length == 0) {
            if(folder.delete()) {
                deletedFiles++;
                return deletedFiles;
            }
        }
        else if(folderContents.length > 0) {

            do {

                File lastFolder = folder;
                File[] lastFolderContents = lastFolder.listFiles();

                //This while loop finds the deepest path that does not contain any other folders
                do {

                    for(File file : lastFolderContents) {

                        if(file.isDirectory()) {
                            lastFolder = file;
                            lastFolderContents = file.listFiles();
                            break;
                        }
                        else {

                            if(file.delete()) {
                                deletedFiles++;
                            }
                            else {
                                break;
                            }

                        }//End if(file.isDirectory())

                    }//End for(File file : folderContents)

                } while(lastFolder.delete() == false);

                deletedFiles++;
                if(folder.exists() == false) {return deletedFiles;}

            } while(folder.exists());
        }
    }
    else {
        return -1;
    }

    return 0;

}

希望这能有所帮助。