android 回调从AsyncTask往Activity传数据

阳光穿透心脏的1/2处 2022-07-18 04:06 89阅读 0赞

1.在LoadTask

( 1

//设置回调借口
    public interface callBack{
        void setItem(Item i);
    }

( 2

//给LoadTask添加设置回调的方法
        public void setCallBack(callBack callback){
            this.callBack = callback;
        }
    ( 3

//LoadTask的参数callBack
        private callBack callBack;
    ( 4 在onPostExecute方法里

if (callBack != null){
                    callBack.setItem(item);
                }
    ( 5 完整的LoadTask

package app.coolwhether.com.weatherapp.Http;
    
    import android.os.AsyncTask;
    import android.util.Log;
    
    import app.coolwhether.com.weatherapp.activity.WeatherShow;
    import app.coolwhether.com.weatherapp.entity.Item;
    import app.coolwhether.com.weatherapp.support.JsonHelper;
    
    /**
     * Created by kirito on 2016/9/4.
     */
    public class LoadTask extends AsyncTask<String,Void,String> {
        private Item item;
        //LoadTask的参数callBack
        private callBack callBack;
        private static final String TAG = "LoadTask";
    
        @Override
        protected String doInBackground(String... params) {
            return Http.getUrlData(params[0]);
        }
    
        @Override
        protected void onPostExecute(String s) {
            //Log.e(TAG, "onPostExecute: s---"+s);
            try{
                item = JsonHelper.parseJsonToItem(s);
                //如果callBack不为空，把item参数传给WeatherShow.activity
                if (callBack != null){
                    callBack.setItem(item);
                }
                Log.e(TAG, "onPostExecute: item---"+item );
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    
        //给LoadTask添加设置回调的方法
        public void setCallBack(callBack callback){
            this.callBack = callback;
        }
    
        //设置回调借口
        public interface callBack{
            void setItem(Item i);
        }
    
    }
    
    2.在需要获取数据的Activity里：

package app.coolwhether.com.weatherapp.activity;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.util.Log;
    import android.widget.TextView;
    
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.net.HttpURLConnection;
    import java.net.URL;
    
    import app.coolwhether.com.weatherapp.Http.Http;
    import app.coolwhether.com.weatherapp.Http.LoadTask;
    import app.coolwhether.com.weatherapp.R;
    import app.coolwhether.com.weatherapp.entity.Item;
    import app.coolwhether.com.weatherapp.support.JsonHelper;
    import butterknife.BindView;
    import butterknife.ButterKnife;
    
    /**
     * Created by kirito on 2016/9/2.
     */
    public class WeatherShow extends AppCompatActivity {
        private String id;
        private static final String path_left = "https://api.heweather.com/x3/weather?cityid=";
        private static final String path_right = "&key=9bb0507d23b046cb9b6fee3c6053f985";
        private String url;
        private Item item;
    
        @BindView(R.id.time_tv_show)
        TextView date_tv;
        @BindView(R.id.wind_sc)
        TextView sc_tv;
        @BindView(R.id.wind_dir)
        TextView dir_tv;
        @BindView(R.id.ss_show)
        TextView ss_tv;
        @BindView(R.id.sr_show)
        TextView sr_tv;
        @BindView(R.id.temp_min_show)
        TextView temp_min_tv;
        @BindView(R.id.temp_max_show)
        TextView temp_max_tv;
        @BindView(R.id.txt_d_show)
        TextView txt_d_tv;
        @BindView(R.id.txt_n_show)
        TextView txt_n_tv;
    
        private static final String TAG = "WeatherShow";
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.weather);
            ButterKnife.bind(this);
    
            setTitle(getIntent().getStringExtra("name"));
            id = getIntent().getStringExtra("id");
            url = path_left + id + path_right;
    
            //new一个LoadTask，设置回调接口，在获取到item后执行与item有关的操作
            //不在获取到item后就使用item会报空指针
            LoadTask task = new LoadTask();
            task.setCallBack(new LoadTask.callBack() {
                @Override
                public void setItem(Item i) {
                    item = i;
                    date_tv.setText(item.getDate());
                    sc_tv.setText(item.getWind_sc());
                    dir_tv.setText(item.getWind_dir());
                    sr_tv.setText(item.getSr());
                    ss_tv.setText(item.getSs());
                    temp_min_tv.setText(item.getTmp_min());
                    temp_max_tv.setText(item.getTmp_max());
                    txt_d_tv.setText(item.getTxt_d());
                    txt_n_tv.setText(item.getTxt_n());
                }
            });
            //执行task
            task.execute(url);
            //new LoadTask().execute(url);
        }
    
       
    }