尝试添加SkyEpub阅读器时出错

Question

这是我试图实现SkyEpub Reader并向其添加书籍的代码。

public boolean makeBooksDirectory() {
        boolean res;
        String filePath = new String(getFilesDir().getAbsolutePath() + "/books");
        Log.d("Debug", filePath);
        File file = new File(filePath);
        if (!file.exists()) {
            res = file.mkdirs();
            Log.d("Land",file.getPath());
        }else {
            res = false;
        }
        return res;
    }

    public boolean fileExists(String fileName) {
        boolean res;

        String pureName = this.removeExtention(fileName);
        String targetDirectory = getFilesDir().getAbsolutePath() + "/books/"+pureName;
        String targetPath = targetDirectory+"/"+ fileName;

        File file = new File(targetPath);
        debug(file.getAbsolutePath());

        if (file.exists()) res = true;
        else  res = false;
        return res;
    }

但是当我试图运行它时，它会显示以下错误。我不明白我是否需要在任何地方制作书籍文件夹？

错误：

I/Timeline: Timeline: Activity_launch_request  D/Debug: /data/user/0/com.App/files/books

08-30 19:43:34.425 15819-15819/com.App D/EPub: faild to make books directory

08-30 19:43:34.457 15819-15819/com.App D/PhoneWindow: notifyNavigationBarColor, color=0x: ff000000, token: android.view.ViewRootImplAO$WEx@4064635

08-30 19:43:34.629 15819-15819/com.App V/ViewRootImpl: Contents drawing finished : com.App/com.App.activities.EPubActivity
08-30 19:43:34.671 15819-15877/com.App E/Surface: getSlotFromBufferLocked: unknown buffer: 0xa5d062e0