android数据存储的四种方案（三）

来源：互联网发布：海康提示网络不可达编辑：程序博客网时间：2024/05/10 13:56

读写Json格式的数据

json格式的数据我们经常用于网络与客户端之间的数据交流，json相对于传统的xml,更加简洁，所以应用也越来越广泛，也常被用于本地存储
Android SDK用于读写JSON格式的数据的主要的两个类：JsonWriter和JsonReader,可以处理json对象和json数组，处理json对象的代码必须放在beginObject方法和endObject方法中，处理json数组的代码必须放在beginArray方法和endArray方法中，看下面代码：

public class TextActivitiy extends Activity{    private String jsonfile = "/sdcard/text.json";    @Override    protected void onCreate(Bundle savedInstanceState) {        // TODO Auto-generated method stub        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_json);    }    private class Product{        public String name;        public String sex;        public Product(String name,String sex){            this.name = name;            this.sex = sex;        }    }    /**     * 将Json对象写入文件     * @param writer     * @param product     * @throws IOException      */    public void writeProduct(JsonWriter writer,Product product) throws IOException{        writer.beginObject();        writer.name("name").value(product.name);        writer.name("sex").value(product.sex);        writer.endObject();    }    /**     * 将Json数组写入文件     * @param writer     * @param products     * @throws IOException     */    public void writeProductArray(JsonWriter writer,List<Product> products) throws IOException{        writer.beginArray();        for(Product product : products){            writeProduct(writer, product);        }        writer.endArray();    }    /**     * 将数组写入OutputStream中     * @param os     * @param products     * @throws IOException     */    public void writeArrayStream(OutputStream os,List<Product> products) throws IOException{        JsonWriter writer = new JsonWriter(new OutputStreamWriter(os));        writer.setIndent(" ");        writeProductArray(writer, products);        writer.close();    }    public void onClick_WriteJSON(View view){        try {            //打开要写入的文件            FileOutputStream fos = new FileOutputStream(jsonfile);            List<Product> products = new ArrayList<Product>();            products.add(new Product("姚化吉", "男"));            products.add(new Product("刘欣煜", "男"));            writeArrayStream(fos, products);            Toast.makeText(getApplicationContext(), "数据写入成功", 1).show();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    /**     * 读取Json对象     * @param reader     * @return     * @throws IOException     */    public Product readProduct(JsonReader reader) throws IOException{        String name = null;        String sex = null;        reader.beginObject();        while(reader.hasNext()){            String role = reader.nextName();            if(role.equals("name")){                name = reader.nextString();            }else if(role.equals("sex")){                sex = reader.nextString();            }else{                reader.skipValue();            }        }        reader.endObject();        return new Product(name, sex);    }    /**     * 读取Json数组     * @param reader     * @return     * @throws IOException     */    public List<Product> readProductArray(JsonReader reader) throws IOException{        List<Product> products = new ArrayList<Product>();        reader.beginArray();        while(reader.hasNext()){            products.add(readProduct(reader));        }        reader.endArray();        return products;    }    /**     * 从文件中读取json数组并转化为List<Product> 对象     * @param in     * @return     * @throws Exception     */    public List<Product> readArrayStream(InputStream in) throws Exception{        JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8"));        try{            return readProductArray(reader);        }finally{            reader.close();        }    }    public void onClick_ReadJSON(View view){        String result = "";        try {            //指定读取json数据的文件路径            FileInputStream fis = new FileInputStream(jsonfile);            List<Product> products = readArrayStream(fis);             if(products != null){                for(Product product : products){                    result += "name:" + product.name + "sex:" + product.sex + "\n";                }                Toast.makeText(getApplicationContext(), result, 2).show();            }        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

这段代码主要是将List数组保存到JSON格式的文件中，再将该文件中的内容读取出来并还原成list数组

1 0