Question

我使用文件编写器以一种类似CSV的格式将对象的arraylist写为文件，作为字符串。无论如何，我有问题让它工作，但现在我得到一个FileNotFound异常，它说在异常中创建的文件是只读的。正如我检查的那样，文件已创建，但显然无法写入。但是我实际上想要覆盖内容，但是会出现这个错误。

        ///Like a CSV file. 
        try{
            FileWriter writer_file = new FileWriter("PeopleDetailsFile");

            String filestring = ""; ///initializes filestring, which is written to the file.
            for(PeopleDetails person : peopledetails_file){
                String person_detail_string = "";
                person_detail_string = person.name + "," + person.number;
                filestring = filestring + person_detail_string + ";";

            }
            writer_file.write(filestring);
            writer_file.close();
        }
            catch (IOException e) {
                Log.e("ERROR", e.toString());

        }finally{
            ///Hopefully won't get an error here.
            Intent switch_menu = new Intent(this, MenuList.class);
            startActivity(switch_menu);
        }

Answer 1

尝试使用PrintWriter。我在下面为您提供了一些简要指南，但需要进行修改。此外，请注意我将名称和数字保存在不同的行中，因此当您阅读详细信息时，您应该使用相同的方法。

 public void writeToFile(String fileName, ArrayList<PeopleDetails> peopledetails) {
        try {
            /*
             * Create a FileWriter object that handles the low-level details of
             * writing
             */
            FileWriter theFile = new FileWriter(fileName);

            /* Create a PrintWriter object to wrap around the FileWriter object */
            /* This allows the use of high-level methods like println */
            PrintWriter fileOut = new PrintWriter(theFile);

            /* Print some lines to the file using the println method */
            for (int i = 0; i < peopledetails.size(); i++) {
                fileOut.println(peopledetails.get(i).getName());
                fileOut.println(peopledetails.get(i).getNumber());
            }
            /* Close the file so that it is no longer accessible to the program */
            fileOut.close();
        }

        /* Handle the exception thrown by the FileWriter methods */
        catch (IOException e) {
            System.out.println("Problem writing to the file");
        }
    } /* End of method writeToFile */

Answer 2

每次要重写时都可以尝试删除文件。尝试{

        File file = new File("PeopleDetailsFile");

        if(file.delete()){
            System.out.println(file.getName() + " is deleted!");
        }else{
            System.out.println("Delete operation is failed.");
        }

    }catch(Exception e){

        e.printStackTrace();

    }

或者：您可以将FileWriter设置为它附加到当前文档的位置：

 FileWriter writer_file = new FileWriter("PeopleDetailsFile", true); //true means append = true;

Answer 3

使用fileName和List作为参数调用此方法。

public void fileWrite(String fileName,ArrayList<PeopleDetails> person){
        File           f ;
        FileWriter     fw = null;
        BufferedWriter bw = null;
        try {
            f  = new File(fileName);
            fw = new FileWriter(f.getAbsoluteFile());
            bw = new BufferedWriter(fw);
            for(PeopleDetails i:person){
                bw.write(i.name+","+i.number+";");
                bw.newLine();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                if(bw!=null)
                    bw.close();
                if(fw!=null)
                    fw.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }   
    }

Answer 4

使用附加标志的FileWriter的其他构造函数：FileWriter（文件文件，布尔附加）

Answer 5

您可能正在尝试写入“root”文件夹。您应该按照Android上下文openFileOutput而不是FileWriter来写入应用程序的目录（而不是根目录）。

根据文件：

打开与此Context的应用程序包关联的私有文件写作。如果文件尚不存在，则创建该文件。

Filewriter创建一个只读的文件

5 个答案: