将JSON写入文件 [英] Write JSON to a File

问题描述

我有一个类compositionJSON.该类具有一个名为makeJSONObject的方法，该方法创建一个JSON-Object并将其放入其中.这是该类的代码.

I have a class compositionJSON. The class has a method calls makeJSONObject, that creates a JSON-Object and put stuff in it. Here is the code of the class.

public class CompositionJso extends JSONObject {



public JSONObject makeJSONObject (String title, String desc, ArrayList<String> imgPath, ArrayList<Resources> imgView) {

    JSONObject obj = new JSONObject() ;

    try {
        obj.put("title", title);
        obj.put("desc", desc);
        obj.put("imgPath", imgPath);
        obj.put("imgViewPath", imgView);
    } catch (JSONException e) {
        e.printStackTrace();
    }

    return obj;
}

现在，我创建此类的一个实例，并在另一个类中调用该方法.之后，我想将JSONObject写入文件并将其保存在设备上的sd卡上.这是代码:

Now I create a instance of this class and call the method in another class. After that I want to write the JSONObject to file and save it on the sd card on device. Here is the code:

 saveCompo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            setName();
            createJSONFolder();
            CompositionJso obj = new CompositionJso();
            obj.makeJSONObject(compoTitle, compoDesc, imgPaths, imageViewPaths);
            MyCompositionsListActivity.buildList();

            try {
                Writer output = null;
                File file = new File("storage/sdcard/MyIdea/MyCompositions/" + compoTitle + ".json");
                output = new BufferedWriter(new FileWriter(file));
                output.write(obj.toString());
                output.close();
                Toast.makeText(getApplicationContext(), "Composition saved", Toast.LENGTH_LONG).show();

            } catch (Exception e) {
                Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
            }
            finish();
        }
    });

文件保存成功，但是如果我打开它，里面什么也没有.代码有什么问题?

The file is saving successfully but if I open it, there is nothing inside. What is wrong with the code?

推荐答案

makeJSONObject返回JSONObject

您的代码应为

saveCompo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            setName();
            createJSONFolder();
            CompositionJso obj = new CompositionJso();
            JSONObject  jsonObject = obj.makeJSONObject(compoTitle, compoDesc, imgPaths, imageViewPaths);
            MyCompositionsListActivity.buildList();

            try {
                Writer output = null;
                File file = new File("storage/sdcard/MyIdea/MyCompositions/" + compoTitle + ".json");
                output = new BufferedWriter(new FileWriter(file));
                output.write(jsonObject.toString());
                output.close();
                Toast.makeText(getApplicationContext(), "Composition saved", Toast.LENGTH_LONG).show();

            } catch (Exception e) {
                Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
            }
            finish();
        }
    });

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