android 项目学习随笔六（网络缓存）

1、 对SharePreference的封装

import android.content.Context;

import android.content.SharedPreferences;

/**

 * 对SharePreference的封装

 *

 *

 */

public class PrefUtils {

    public static void putBoolean(String key, boolean value, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        sp.edit().putBoolean(key, value).commit();

    }

    public static boolean getBoolean(String key, boolean defValue, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        return sp.getBoolean(key, defValue);

    }

    public static void putString(String key, String value, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        sp.edit().putString(key, value).commit();

    }

    public static String getString(String key, String defValue, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        return sp.getString(key, defValue);

    }

    public static void putInt(String key, int value, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        sp.edit().putInt(key, value).commit();

    }

    public static int getInt(String key, int defValue, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        return sp.getInt(key, defValue);

    }

    public static void remove(String key, Context ctx) {

        SharedPreferences sp = ctx.getSharedPreferences("config",

                Context.MODE_PRIVATE);

        sp.edit().remove(key).commit();

    }

}

2、 网络缓存工具类

import android.content.Context;

/**

 * 网络缓存工具类

 * 原则:

 * 以url+参数为key, 以json为value,保存起来

 *

 */

public class CacheUtils {

    /**

     * 写缓存

     */

    public static void setCache(String url, String json, Context ctx) {

        //有时候,可以将缓存写在本地文件中, 以MD5(url)为文件名, 以json为文件内容保存

        PrefUtils.putString(url, json, ctx);

    }

    /**

     * 读缓存

     */

    public static String getCache(String url, Context ctx) {

        //如果缓存写在文件中, 先找文件MD5(url)存不存在,如果存在,说明有缓存

        return PrefUtils.getString(url, null, ctx);

    }

}

3、新闻中心示例

import java.util.ArrayList;

import android.app.Activity;

import android.text.TextUtils;

import android.widget.Toast;

import com.google.gson.Gson;

import com.itheima.zhsh66.MainActivity;

import com.itheima.zhsh66.base.BaseMenuDetailPager;

import com.itheima.zhsh66.base.BasePager;

import com.itheima.zhsh66.base.impl.menudetail.InteractMenuDetailPager;

import com.itheima.zhsh66.base.impl.menudetail.NewsMenuDetailPager;

import com.itheima.zhsh66.base.impl.menudetail.PhotosMenuDetailPager;

import com.itheima.zhsh66.base.impl.menudetail.TopicMenuDetailPager;

import com.itheima.zhsh66.domain.NewsMenuData;

import com.itheima.zhsh66.global.Constants;

import com.itheima.zhsh66.utils.CacheUtils;

import com.lidroid.xutils.HttpUtils;

import com.lidroid.xutils.exception.HttpException;

import com.lidroid.xutils.http.ResponseInfo;

import com.lidroid.xutils.http.callback.RequestCallBack;

import com.lidroid.xutils.http.client.HttpRequest.HttpMethod;

/**

 * 新闻中心

 *

 */

public class NewsCenterPager extends BasePager {

    // 菜单详情页集合

    private ArrayList<BaseMenuDetailPager> mMenuDetailPagers;

    private NewsMenuData mNewsMenuData;// 新闻分类信息网络数据

    public NewsCenterPager(Activity activity) {

        super(activity);

    }

    @Override

    public void initData() {

        System.out.println("新闻中心初始化...");

        tvTitle.setText("新闻");

        // 1.首先先看本地有没有缓存

        // 2.有缓存,直接加载缓存

        String cache = CacheUtils.getCache(Constants.CATEGORIES_URL, mActivity);

        if (!TextUtils.isEmpty(cache)) {

            // 有缓存

            System.out.println("发现缓存....");

            processResult(cache);

        }

        // 即使发现有缓存,仍继续调用网络, 获取最新数据

        getDataFromServer();

    }

    /**

     * 从服务器获取数据 需要权限: <uses-permission

     * android:name="android.permission.INTERNET"/>

     */

    private void getDataFromServer() {

        HttpUtils utils = new HttpUtils();

        utils.send(HttpMethod.GET, Constants.CATEGORIES_URL,

                new RequestCallBack<String>() {

                    @Override

                    public void onSuccess(ResponseInfo<String> responseInfo) {

                        // 请求成功

                        String result = responseInfo.result;// 获取json字符串

                        // System.out.println("result:" + result);

                        processResult(result);

                        // 写缓存

                        CacheUtils.setCache(Constants.CATEGORIES_URL, result,

                                mActivity);

                    }

                    @Override

                    public void onFailure(HttpException error, String msg) {

                        // 请求失败

                        error.printStackTrace();

                        Toast.makeText(mActivity, msg, Toast.LENGTH_SHORT)

                                .show();

                    }

                });

    }

    /**

     * 解析json数据

     *

     * @param result

     */

    protected void processResult(String result) {

        // gson->json

        Gson gson = new Gson();

        mNewsMenuData = gson.fromJson(result, NewsMenuData.class);

        System.out.println("解析结果:" + mNewsMenuData);

        // 获取侧边栏对象

        MainActivity mainUI = (MainActivity) mActivity;

        LeftMenuFragment leftMenuFragment = mainUI.getLeftMenuFragment();

        // 将网络数据设置给侧边栏

        leftMenuFragment.setData(mNewsMenuData.data);

        // 初始化4个菜单详情页

        mMenuDetailPagers = new ArrayList<BaseMenuDetailPager>();

        mMenuDetailPagers.add(new NewsMenuDetailPager(mActivity,

                mNewsMenuData.data.get(0).children));

        mMenuDetailPagers.add(new TopicMenuDetailPager(mActivity));

        mMenuDetailPagers.add(new PhotosMenuDetailPager(mActivity));

        mMenuDetailPagers.add(new InteractMenuDetailPager(mActivity));

        // 菜单详情页-新闻作为初始页面

        setCurrentMenuDetailPager(0);

    }

    // 给新闻中心页面的FrameLayout填充布局

    protected void setCurrentMenuDetailPager(int position) {

        BaseMenuDetailPager pager = mMenuDetailPagers.get(position);

        // 移除之前所有的view对象, 清理屏幕

        flContent.removeAllViews();

        flContent.addView(pager.mRootView);

        pager.initData();// 初始化数据

        // 更改标题

        tvTitle.setText(mNewsMenuData.data.get(position).title);

    }

}