android 项目学习随笔六（网络缓存）

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();
}
}

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);
}
}

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);
}

}