使用Handle进行Gson解析及开子线程从网络获得数据

Handle与AsyncTask都是做耗时操作时所需的事件，这里我们重点展示Handle的用法

需求

/**
 * 使用异步任务Handler从给定的网址http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=20&page=1
 * 中下载一个json字符串。使用Gson解析下载下来的json字符串。
 将解析出的title列使用Spinner进行展示。弹出选中项的内容
 */

需要注意的是，在使用Gson是需要进行导包

在里面找GSON包后确定即可，下面是具体代码（要注意的是，全局的string内的内容需要有自己的接口，并不是固定的）

MainActivity

public class MainActivity extends AppCompatActivity {
    private Spinner sp;
    String url="http://169.254.167.244:8080/Web_Data/foot.txt";
    Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sp=(Spinner)findViewById(R.id.sp);
        handler=new Handler(){
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                if(msg.what==100){
                    String json = msg.obj.toString();
                    Gson gson=new Gson();
                    Food food = gson.fromJson(json, Food.class);
                    List list=new ArrayList<>();
                    for (int i=0;i adapter=new ArrayAdapter(MainActivity.this,android.R.layout.simple_list_item_1,list);
                    sp.setAdapter(adapter);
                    sp.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                        @Override
                        public void onItemSelected(AdapterView parent, View view, int position, long id) {
                            Toast.makeText(MainActivity.this,sp.getSelectedItem().toString(),Toast.LENGTH_LONG).show();
                        }

                        @Override
                        public void onNothingSelected(AdapterView parent) {

                        }
                    });
                }
            }
        };

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    URL url1=new URL(url);
                    HttpURLConnection huc=(HttpURLConnection)url1.openConnection();
                    huc.setConnectTimeout(3000);
                    huc.connect();
                    if(huc.getResponseCode()==200){
                        InputStream inputStream = huc.getInputStream();
                        byte[] b=new byte[1024];
                        int len=0;
                        StringBuilder sb=new StringBuilder();
                        while ((len=inputStream.read(b))!=-1){
                            sb.append(new String(b,0,len));
                        }
                        String json = sb.toString();
                        Message mess=Message.obtain();
                        mess.obj=json;
                        mess.what=100;
                        handler.sendMessage(mess);

                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }).start();
    }

}

写完主Activity后需要建一个接口的实体类方便之后用做泛型等操作，实体类的快捷方法在之前的Gson这篇文章中有讲解

实体类

public class Food {

    /**
     * ret : 1
     * data : [{"id":"8289","title":"油焖大虾","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/9/8289.jpg","collect_num":"1635","food_str":"大虾 葱 生姜 植物油 料酒","num":1635},{"id":"2127","title":"四川回锅肉","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2127.jpg","collect_num":"1572","food_str":"猪肉 青蒜 青椒 红椒 姜片","num":1572},{"id":"30630","title":"超简单芒果布丁","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/31/30630.jpg","collect_num":"1502","food_str":"QQ糖 牛奶 芒果","num":1502},{"id":"9073","title":"家常红烧鱼","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/10/9073.jpg","collect_num":"1408","food_str":"鲜鱼 姜 葱 蒜 花椒","num":1408},{"id":"10097","title":"家常煎豆腐","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10097.jpg","collect_num":"1393","food_str":"豆腐 新鲜红椒 青椒 葱花 油","num":1393},{"id":"10509","title":"水煮肉片","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10509.jpg","collect_num":"1325","food_str":"瘦猪肉 生菜 豆瓣酱 干辣椒 花椒","num":1325},{"id":"46968","title":"红糖苹果银耳汤","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/47/46968.jpg","collect_num":"1235","food_str":"银耳 苹果 红糖","num":1235},{"id":"10191","title":"麻婆豆腐","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10191.jpg","collect_num":"1203","food_str":"豆腐 肉末 生抽 白糖 芝麻油","num":1203},{"id":"2372","title":"皮蛋瘦肉粥","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2372.jpg","collect_num":"1135","food_str":"大米 皮蛋 猪肉 油条 香葱","num":1135},{"id":"2166","title":"蚂蚁上树","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2166.jpg","collect_num":"1126","food_str":"红薯粉 肉 姜 蒜 花椒","num":1126},{"id":"2262","title":"糖醋肉","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2262.jpg","collect_num":"1063","food_str":"猪肉 红椒 黄椒 洋葱 蛋清","num":1063},{"id":"9971","title":"鱼香豆腐","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/10/9971.jpg","collect_num":"996","food_str":"豆腐 木耳 胡萝卜 香葱 番茄酱","num":996},{"id":"10172","title":"干煸四季豆","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10172.jpg","collect_num":"982","food_str":"四季豆 干辣椒 蒜头 酱油 糖","num":982},{"id":"2685","title":"胡萝卜肉末蒸蛋","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2685.jpg","collect_num":"896","food_str":"胡萝卜 肉 蛋 生抽 盐","num":896},{"id":"9972","title":"虎皮青椒","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/10/9972.jpg","collect_num":"879","food_str":"青辣椒 大蒜 香醋 白糖 生抽","num":879},{"id":"10437","title":"叉烧排骨","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10437.jpg","collect_num":"791","food_str":"排骨 李锦记叉烧酱 植物油 清水 油菜","num":791},{"id":"2348","title":"麻辣肉丝面","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2348.jpg","collect_num":"748","food_str":"面条 肉丝 淀粉 酱油 辣椒","num":748},{"id":"2892","title":"\u201c五行\u201d彩蔬汤","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/3/2892.jpg","collect_num":"747","food_str":"黑木耳 玉米 牛蒡 胡萝卜 西兰花","num":747},{"id":"10044","title":"土豆炖翅根","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/11/10044.jpg","collect_num":"745","food_str":"土豆 翅根 葱 姜 料酒","num":745},{"id":"33783","title":"美人豆浆","pic":"http://www.qubaobei.com/ios/cf/uploadfile/132/34/33783.jpg","collect_num":"743","food_str":"黄豆 红豆 绿豆 黑豆 黑米","num":743}]
     */

    private int ret;
    private List data;

    public int getRet() {
        return ret;
    }

    public void setRet(int ret) {
        this.ret = ret;
    }

    public List getData() {
        return data;
    }

    public void setData(List data) {
        this.data = data;
    }

    public static class DataBean {
        /**
         * id : 8289
         * title : 油焖大虾
         * pic : http://www.qubaobei.com/ios/cf/uploadfile/132/9/8289.jpg
         * collect_num : 1635
         * food_str : 大虾 葱 生姜 植物油 料酒
         * num : 1635
         */

        private String id;
        private String title;
        private String pic;
        private String collect_num;
        private String food_str;
        private int num;

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public String getPic() {
            return pic;
        }

        public void setPic(String pic) {
            this.pic = pic;
        }

        public String getCollect_num() {
            return collect_num;
        }

        public void setCollect_num(String collect_num) {
            this.collect_num = collect_num;
        }

        public String getFood_str() {
            return food_str;
        }

        public void setFood_str(String food_str) {
            this.food_str = food_str;
        }

        public int getNum() {
            return num;
        }

        public void setNum(int num) {
            this.num = num;
        }
    }
}

这就是具体的逻辑代码，接下来是布局xml，非常简单，只需一个Spinner