在安卓中写入JSON文件时出现问题。

huangapple
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英文:

Issue writing to json file in android

问题

我尝试写入一个 JSON 文件，但它就是不起作用，我没有收到任何错误消息，但文件中什么也没有改变。

以下是我的代码的相关部分：

  1. try {
  2.     // 方法1
  3.     Gson gson = new Gson();
  4.     String s = "gjsanhfhj";
  5.     String path = this.getApplicationContext().getFilesDir().getAbsolutePath() + "/" + "test.json";
  7.     File file = new File(path);
  8.     file.setWritable(true);
  10.     gson.toJson(s, new FileWriter(file));
  12.     // 方法2
  13.     FileOutputStream outputStream;
  14.     outputStream = openFileOutput(path, Context.MODE_PRIVATE);
  15.     outputStream.write(s.getBytes());
  16.     outputStream.close();
  18.     // 方法3
  19.     Writer output;
  20.     output = new BufferedWriter(new FileWriter(file));
  21.     output.write(s);
  22.     output.close();
  24.     Toast.makeText(this.getApplicationContext(), "check", Toast.LENGTH_SHORT).show();
  26. } catch (Exception e) {
  27.     e.printStackTrace();
  28. }

我尝试了上面的三种方法，但都没有起作用，我找不到其他解决方法。

我还尝试了以下代码：

  1. public class PlayerData {
  2.     private int gold;
  3.     private int wins;
  4.     private int losses;
  6.     public PlayerData(){
  7.         gold = 0;
  8.         wins = 0;
  9.         losses = 0;
  10.     }
  12.     Gson gson = new Gson();
  13.     String path = this.getApplicationContext().getFilesDir().getAbsolutePath() + "/" + "test.json";
  14.     File file = new File(path);
  15.     file.setWritable(true);
  17.     gson.toJson(new PlayerData(), new FileWriter(file));

但也没有成功。

英文:

Im trying to write into a json file and it just doesnt work, I dont get any errors but nothing changes in the file.

here is the relevant section of my code

  1.         try {
  2.             //method1
  3.             Gson gson = new Gson();
  4.             String s = "gjsanhfhj";
  5.             String path = this.getApplicationContext().getFilesDir().getAbsolutePath() + "/" + "test.json";
  7.             File file = new File(path);
  8.             file.setWritable(true);
  10.             gson.toJson(s,new FileWriter(file));
  12.             //method2
  13.             FileOutputStream outputStream;
  14.             outputStream = openFileOutput(path, Context.MODE_PRIVATE);
  15.             outputStream.write(s.getBytes());
  16.             outputStream.close();
  18.             //method3
  19.             Writer output;
  20.             output = new BufferedWriter(new FileWriter(file));
  21.             output.write(s);
  22.             output.close();
  25.             Toast.makeText(this.getApplicationContext(), "check", Toast.LENGTH_SHORT).show();
  27.         } catch (Exception e) {
  28.             e.printStackTrace();
  29.         }

I tried the 3 methods above, didnt work I couldnt find anything else

I tried this

  2. public class PlayerData {
  3.     private int gold;
  4.     private int wins;
  5.     private int losses;
  7.     public PlayerData(){
  8.         gold = 0;
  9.         wins = 0;
  10.         losses = 0;
  11.     }
  14.             Gson gson = new Gson();
  15.             String path = this.getApplicationContext().getFilesDir().getAbsolutePath() + "/" + "test.json";
  16.             File file = new File(path);
  17.             file.setWritable(true);
  19.             gson.toJson(new PlayerData(),new FileWriter(file));

didnt work

答案1

得分: 0

Gson.toJson(Obj)用于将对象转换为一个键值对的Json字符串。Gson.toJson()接受一个Java对象作为参数，而您传递的是一个字符串值，这不正确，我认为。例如，Employee类的对象可以转换为以下json。

  1. class Employee {
  2.     int empId;
  3.     String name;
  4.     String department;   
  5. }

现在，您可以调用：

  1. gson.toJson(new Employee(100, "abc", "xyz"), new FileWriter(file));

所以，请再次检查您的需求。

英文:

Gson.toJson(Obj) is used to convert an object into a Json-String which is a key value pair. Gson.toJson() takes a java object as an argument, whereas, you are passing a STRING value which not right, I think. For example, an object of Employee class, can be converted into json as below.

  1. class Employee {
  2. int empId;
  3. String name;
  4. String department;

} `

Now, you can call

  1. gson.toJson(new Employee(100, "abc", "xyz"), new FileWriter(file));

So, please check your requirement again.

答案2

得分: 0

以下是翻译好的代码部分：

  1. 尝试这个。这对我有效。
  3. private class myString {
  4.     String str;
  5.     public myString() {
  6.         this.str = "Testing123...";
  7.     }
  8. }
  10. Gson gson = new Gson();
  11. myString s = new myString();
  12. File file = new File(getApplicationContext().getFilesDir(), "Test.json");
  14. try {
  15.     if(!file.exists())
  16.         file.createNewFile();
  17.     FileOutputStream fileOutputStream = new FileOutputStream(file);
  18.     byte[] arr = gson.toJson(s).getBytes();
  19.     fileOutputStream.write(arr);
  20.     fileOutputStream.close();
  21. } catch (IOException e) {
  22.     e.printStackTrace();
  23. }

如果您有任何其他需要，请随时告诉我。

英文:

Try this. This worked for me.

  1. private class myString {
  2.     String str;
  3.     public myString() {
  4.         this.str = "Testing123...";
  5.     }
  6. }
  8. Gson gson = new Gson();
  9.     myString s = new myString();
  10.     File file = new File(getApplicationContext().getFilesDir(), "Test.json");
  12.     try {
  13.         if(!file.exists())
  14.             file.createNewFile();
  15.         FileOutputStream fileOutputStream = new FileOutputStream(file);
  16.         byte[] arr = gson.toJson(s).getBytes();
  17.         fileOutputStream.write(arr);
  18.         fileOutputStream.close();
  19.     } catch (IOException e) {
  20.         e.printStackTrace();
  21.     }
  22. }

huangapple
  • 本文由 发表于 2023年4月20日 08:04:06
  • 转载请务必保留本文链接：https://go.coder-hub.com/76059630.html
  • android
  • java
  • json
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