Android -文件读写

Question

我是Android程序的初学者。我试图提供一个表单给用户输入一些信息。我想将这些信息写入文件中，然后从文件中读取并在TextView中显示。目前，我读到的是null。你能帮我解决这个问题吗？代码是这个：

submit.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // write
        StringBuilder s = new StringBuilder();
        s.append("Event name: " + editText1.getText() + "|");
        s.append("Date: " + editText2.getText() +  "|");
        s.append("Details: " + editText3.getText() + "|");

        String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
        File file= new File(extStorageDirectory, "config.txt");
        try {
            writeToFile(s.toString().getBytes(), file);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // read from file and show in text view
        Context context = getApplicationContext();
        String filename = "config.txt";
        String str = readFromFile(context, filename);
        String first = "You have inputted: \n";
        first += str;
        textView.setText(first);

    }
});

编写功能：

public static void writeToFile(byte[] data, File file) throws IOException {
    BufferedOutputStream bos = null;
    try {
        FileOutputStream fos = new FileOutputStream(file);
        bos = new BufferedOutputStream(fos);
        bos.write(data);
    }
    finally {
        if (bos != null) {
            try {
                bos.flush ();
                bos.close ();
            }
            catch (Exception e) {
            }
        }
    }
}   

阅读功能：

public String readFromFile(Context context, String filename) {
    try {
        FileInputStream fis = context.openFileInput(filename);
        InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
        BufferedReader bufferedReader = new BufferedReader(isr);
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            sb.append(line).append("\n");
        }
        return sb.toString();
    } catch (FileNotFoundException e) {
        return "";
    } catch (UnsupportedEncodingException e) {
        return "";
    } catch (IOException e) {
        return "";
    }
}

Answer 1

Edittext的getText()方法返回editable。因此，首先应该使用toString()函数将其转换为字符串。并检查您是否已给予WRITE_EXTERNAL_STORAGE许可。

Answer 2

如果我没有遗漏你写的东西

String extStorageDirectory = 
Environment.getExternalStorageDirectory().toString();
File file= new File(extStorageDirectory, "config.txt");

但你读到了

FileInputStream fis = context.openFileInput(filename);

后者在应用程序基目录中使用dir，而输出则转到外部strage目录的基dir。

为什么不使用context.openFileOutput()而不是getExternalStorageDirectory()

如果文件应该存储在外部，请尝试如下:创建File对象的方式保持不变。请使用FileOutputStream fos = new FileOutputStream(file);代替FileInputStream (用于写作)。请记住在清单中设置适当的权限。在哪些条件下，它们是必要的，请咨询Android文档。