用異步任務實現簡單的新聞資訊

程序中用到的有接口回調，接口回調在開發中是很重要的，能解決很多問題，如果有不懂得，可以繼續關注我的博客，部分博客中有我對於接口回調的理解，我會後續會寫更多的博客，我的技術有限，所以代碼都是以簡單的爲主，異步任務有不懂得，我的博客也有關於異步任務的一些介紹
值得注意的是：本程序的接口並沒有寫，讀者可自己尋找適合的接口進行操作

新聞資訊的基本佈局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="${packageName}.${activityClass}" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="新聞標題：" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="請點擊：" />

        <Spinner
            android:id="@+id/sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@null" />
    </LinearLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="20dp"
        android:background="#00BFFF" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10px"
        android:text="新聞內容：" />

    <TextView
        android:id="@+id/te"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

封裝好的異步任務工具類

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import javax.security.auth.PrivateCredentialPermission;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;

public class PottingAsyncTask extends AsyncTask<String, Void, Object> {

    private OnDownLitener onDownLitener;
    private DownType downType;
    public PottingAsyncTask(DownType downType) {
        // TODO Auto-generated constructor stub
        this.downType = downType;
    }
    //子線程
    @Override
    protected Object doInBackground(String... arg0) {
        // TODO Auto-generated method stub
        byte[] bs = getByteArray(arg0[0]);
        if (bs != null) {
            switch (downType) {
            case JSON:
                String json = new String(bs);
                if(onDownLitener!=null){                    
                    Object datasObject=onDownLitener.downJson(json);
                    return datasObject;
                }
                break;
            case IMAGE:
                Bitmap bitmap = BitmapFactory.decodeByteArray(bs, 0, bs.length);
                return bitmap;
            default:
                break;
            }
        }
        return null;
    }
    //在執行完doInBackground後再執行onPostExecute
    @Override
    protected void onPostExecute(Object result) {
        switch (downType) {
        case JSON:
            if(onDownLitener!=null){
                onDownLitener.paresJson(result);
            }
            break;
        case IMAGE:
            if(onDownLitener!=null){
                onDownLitener.setImage(result);
            }
            break;
        default:
            break;
        }
    }
    //構建接口,使用接口回調的方式控制控件
    public interface OnDownLitener{
        Object downJson(String json);//用於下載json
        void paresJson(Object object);//用於解析json
        void setImage(Object object);//用於控制image控件
    }
    //獲得byte數組
    private byte[] getByteArray(String urlString) {
        InputStream in = null;
        ByteArrayOutputStream ou = null;
        URL url;
        try {
            url = new URL(urlString);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url
                    .openConnection();
            httpURLConnection.setRequestMethod("GET");
            httpURLConnection.setReadTimeout(3000);
            httpURLConnection.connect();
            if (httpURLConnection.getResponseCode() == 200) {

                in = httpURLConnection.getInputStream();
                ou=new ByteArrayOutputStream();
                byte[] buffer = new byte[1024 * 8];
                int len = -1;

                while ((len = in.read(buffer)) != -1) {
                    ou.write(buffer, 0, len);
                }
                return ou.toByteArray();
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if (ou != null) {
                try {
                    ou.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
    //藉助泛型，確定所需要的類型
    public static enum DownType {
        JSON, IMAGE
    }
    //接口回調的方法
    public PottingAsyncTask setOnDownLitener(OnDownLitener onDownLitener) {
        this.onDownLitener = onDownLitener;
        return this;//返回this的原因是鏈式編程，返回當前PottingAsyncTask的對象
    }
}

新聞資訊的主方法

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.example.day06_04.PottingAsyncTask.DownType;
import com.example.day06_04.PottingAsyncTask.OnDownLitener;

import android.R.integer;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.Spinner;
import android.widget.TextView;

public class MainActivity extends Activity {
    //需要自己填寫自己所需要的新聞接口
    String urlString="";
    private Spinner spinner=null;
    private TextView textView=null;
    private ArrayAdapter<String> adapter=null;
    private List<Map<String, Object>> listmap=new ArrayList<Map<String,Object>>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView=(TextView) findViewById(R.id.te);
        spinner=(Spinner) findViewById(R.id.sp);

        spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1,
                    int arg2, long arg3) {
                // 判斷是否等於空的原因是因爲網絡加載時需要時間的，防止程序報錯
                if(listmap!=null){
                    String dString=(String) listmap.get(arg2).get("summary");
                    textView.setText(dString);  
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {
            }
        });

        new PottingAsyncTask(DownType.JSON).setOnDownLitener(new OnDownLitener() {

            @Override
            public void paresJson(Object object) {
                // TODO Auto-generated method stub
                List<String> list =(List<String>) object;
                adapter=new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item,list);
                spinner.setAdapter(adapter);
            }

            @Override
            public Object downJson(String json) {
                // TODO Auto-generated method stub
                try {
                //不同的接口，獲得不同的json，所以解析json的代碼也是不一樣的，可以仿造這部分的代碼
                    List<String> list=new ArrayList<String>();
                    JSONObject jsonObject=new JSONObject(json);
                    JSONArray jsonArray=jsonObject.getJSONArray("data");
                    for(int i=0;i<jsonArray.length();i++){
                    //利用Map原因是map可以存儲更多類型的數據
                        Map<String, Object> map=new HashMap<String, Object>();
                        String title = jsonArray.getJSONObject(i).getString("title");
                        String summary = jsonArray.getJSONObject(i).getString("summary");
                        int len=i+1;
                        list.add("【"+len+"】:"+title);
                        map.put("title", title);
                        map.put("summary", summary);
                        listmap.add(map);
                    }
                    return list;                
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                return null;
            }

            @Override
            public void setImage(Object object) {
                // TODO Auto-generated method stub

            }
        }).execute(urlString);
    }
}