Asynctask獲取網絡數據使用

主界面代碼如下，僅僅爲了記錄Asynctask的使用。業務代碼寫在Activity裏面肯定不好的。最好使用MVP模式來實現。

publicclass MainActivity extendsActivity {
    privatestatic String url = "http://www.imooc.com/api/teacher?type=2&num=100";
    privateListView myListView;
 
    @Override
    protectedvoid onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myListView = (ListView) findViewById(R.id.myListView);
        newMyAsynctask().execute(url);
    }
 
    /**
     * 實現網絡的異步訪問
     *
     * @author Administrator
     *
     */
    classMyAsynctask extendsAsyncTask<String, Void, List<NewsBean>> {
 
        @Override
        protectedList<NewsBean> doInBackground(String... params) {
            returngetNetWorkDatas(params[0]);
        }
 
        @Override
        protectedvoid onPostExecute(List<NewsBean> result) {
            super.onPostExecute(result);
            NewsAdapter adapter = newNewsAdapter(result,
                    getApplicationContext());
            myListView.setAdapter(adapter);
        }
 
    }
    /**
     * 獲取制定的 json 數據轉換成我們需要的 NewsBean 對象
     *
     * @param url
     * @return
     */
 
    publicList<NewsBean> getNetWorkDatas(String url) {
        List<NewsBean> myList = newArrayList<>();
        try{
            String jsonString = getJsonString(newURL(url).openStream());
            Log.i("sdaf", jsonString.toString());
            JSONObject jsonObject;
            jsonObject = newJSONObject(jsonString);
            JSONArray array = jsonObject.getJSONArray("data");
            for(inti = 0; i < array.length(); i++) {
                NewsBean bean = newNewsBean();
                JSONObject obj = array.getJSONObject(i);
                bean.image_icon = obj.getString("picSmall");
                bean.title = obj.getString("name");
                bean.content = obj.getString("description");
                myList.add(bean);
            }
        }catch(MalformedURLException e) {
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }catch(JSONException e) {
            e.printStackTrace();
        }
        returnmyList;
    }
 
    /**
     * 獲取返回的String 數據
     *
     * @param is
     * @return
     */
    publicString getJsonString(InputStream is) {
        String result = "";
        InputStreamReader isr;
        try{
            String line = "";
            isr = newInputStreamReader(is, "UTF-8");
            BufferedReader br = newBufferedReader(isr);
            while((line = br.readLine()) != null) {
                result += line;
            }
        }catch(UnsupportedEncodingException e1) {
            e1.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }
        returnresult;
    }
}




適配器代碼如下，可以參考開源的一些全能適配器。

publicclassNewsAdapter extendsBaseAdapter {
    privateList<NewsBean> datas;
    privateContext context;
 
    publicNewsAdapter(List<NewsBean> datas, Context context) {
        super();
        this.datas = datas;
        this.context = context;
    }
 
    @Override
    publicintgetCount() {
        returndatas.size();
    }
 
    @Override
    publicObject getItem(intposition) {
        returndatas.get(position);
    }
 
    @Override
    publiclonggetItemId(intposition) {
        returnposition;
    }
 
    @Override
    publicView getView(intposition, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if(convertView == null) {
            viewHolder = newViewHolder();
            convertView = LayoutInflater.from(context).inflate(
                    R.layout.item_class,null);
            viewHolder.title = (TextView) convertView
                    .findViewById(R.id.tv_title);
            viewHolder.content = (TextView) convertView
                    .findViewById(R.id.tv_content);
            viewHolder.iv_icon = (ImageView) convertView
                    .findViewById(R.id.iv_icon);
            convertView.setTag(viewHolder);
        }else{
            viewHolder = (ViewHolder) convertView.getTag();
        }
        NewsBean bean = datas.get(position);
        viewHolder.iv_icon.setImageResource(R.drawable.ic_launcher);
        String url = bean.image_icon;
        viewHolder.iv_icon.setTag(url);
        // new ImageLoader().showImageByThread(viewHolder.iv_icon,
        // bean.image_icon);
        newImageLoader().showImageByAsyncTask(viewHolder.iv_icon, url);
        viewHolder.title.setText(bean.title);
        viewHolder.content.setText(bean.content);
 
        returnconvertView;
    }
 
    classViewHolder {
        publicTextView title;
        publicTextView content;
        publicImageView iv_icon;
    }
 
}

ImageLoader代碼如下，可以參考其他開源庫（Glide Picasso Fresco）

publicclassImageLoader {
    privateString murl;
    privateImageView imageview;
    privateHandler handler = newHandler() {
        publicvoidhandleMessage(android.os.Message msg) {
            super.handleMessage(msg);
            if(imageview.getTag().equals(murl)) {
                imageview.setImageBitmap((Bitmap) msg.obj);
            }
        };
    };
 
    publicvoidshowImageByThread(ImageView imageView, finalString url) {
        imageview = imageView;
        murl = url;
        newThread() {
            @Override
            publicvoidrun() {
                super.run();
                Bitmap bitmap = getBitMapByUrl(url);
                Message msg = Message.obtain();
                msg.obj = bitmap;
                handler.sendMessage(msg);
            };
        }.start();
    }
 
    publicBitmap getBitMapByUrl(String url) {
        Bitmap bitmap;
        InputStream is = null;
        try{
            URL ul = newURL(url);
            HttpURLConnection connection = (HttpURLConnection) ul
                    .openConnection();
            is = newBufferedInputStream(connection.getInputStream());
            bitmap = BitmapFactory.decodeStream(is);
            connection.disconnect();
            Thread.sleep(1000);
            returnbitmap;
        }catch(MalformedURLException e) {
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }catch(InterruptedException e) {
            e.printStackTrace();
        }finally{
            try{
                is.close();
            }catch(IOException e) {
                e.printStackTrace();
            }
        }
        returnnull;
    }
 
    publicvoidshowImageByAsyncTask(ImageView imageView, String url) {
        newNewsAsyncTask(imageView,url).execute(url);
    }
 
    privateclassNewsAsyncTask extendsAsyncTask<String, Void, Bitmap> {
        privateImageView mimageview;
        privateString mUrl;
        publicNewsAsyncTask(ImageView imageview,String url) {
            mimageview = imageview;
            mUrl= url;
        }
 
        @Override
        protectedBitmap doInBackground(String... arg0) {
 
            returngetBitMapByUrl(arg0[0]);
        }
 
        @Override
        protectedvoidonPostExecute(Bitmap result) {
            super.onPostExecute(result);
            if(mimageview.getTag().equals(mUrl)) {
                mimageview .setImageBitmap(result);
            }
        }
    }
}



publicclassNewsBean {
    publicString title;
    publicString content;
    publicString image_icon;
}