Android 离线app实现

最近公司要弄一个离线的app

实现思路：先加载本地数据如果没有则使用开始使用网络加载，如果加载成功后，之后就可以一直使用本地数据。

MainActivity.java

    /**
     * 获取本地数据，如果本地没有数据则通过网络获取
     */
    private void loadData() {
        String skinCareIndexJson = CacheUtils.readJson("index.json");
        if (!StrUtil.isEmpty(skinCareIndexJson) && !CacheUtils.isCacheDataFailure("index.json")) {
            try {
                parseJson(new JSONObject(skinCareIndexJson));
            } catch (JSONException e) {
                e.printStackTrace();
                loadHttpData();
            }
        } else {
            loadHttpData();
        }
    }

    /**
     * 通过网络获取数据
     */
    private void loadHttpData() {
        if (hasInternet()) {
            HttpRestClient.post(Urls.INDEX + "userId=" + PreferencesUtil.getUserPreferences(UserPref.UserId), null, new JsonHttpResponseCallback() {
                @Override
                public void callback(int statusCode, JSONObject response) {
                    if (response == null) {
                        AppManager.showToastMessage("视频获取数据失败~！");
                        mTopImageLoopAdapter.notifyDataSetChanged();
                        return;
                    }
                    int result = response.optInt("result");
                    if (result == 0) {
                        AppManager.showToastMessage(response.optString("info"));
                        mTopImageLoopAdapter.notifyDataSetChanged();
                        return;
                    }
                    JSONObject datas = response.optJSONObject("datas");
                    parseJson(datas);
                    CacheUtils.writeJson(datas.toString(), "index.json");
                }
            });
        } else {
            AppManager.showToastMessage(getResources().getString(R.string.internet_error));
            mTopImageLoopAdapter.notifyDataSetChanged();
        }

    }

    private void parseJson(JSONObject datas){
        hotFlagVideoList.clear();
        hotFlagVideoList.addAll(JsonUtil.getListFromJSON(datas.optJSONArray("hotFlagVideoList"), Video[].class));
        mTopImageLoopAdapter.notifyDataSetChanged();
    }

CacheUtils.java

package com.mlx.lhsc.util;

import android.os.Environment;
import android.util.Log;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;

public class CacheUtils {
    public static int CACHE_TIME_DAY_NUM = 7;
    public static int CACHE_TIME_ONE_DAY = 1000 * 60 * 60 * 24 * CACHE_TIME_DAY_NUM;
    private static BufferedWriter bw = null;
    private static BufferedReader br = null;


    /**
     * 判断文件缓存是否过期
     *
     * @param fileName
     * @return true 为过期
     */
    public static boolean isCacheDataFailure(String fileName) {
        String cacheRoot = Environment.getExternalStorageDirectory().getAbsolutePath() + "/LDM/json/";
        File file = new File(cacheRoot);
        if (!file.exists()) {
            file.mkdirs();
        }
        File data = new File(cacheRoot, fileName);
        boolean failure = false;
        if ((System.currentTimeMillis() - data.lastModified()) > CACHE_TIME_ONE_DAY)
            failure = true;
        else if (!data.exists())
            failure = true;
        return failure;
    }

    /**
     * 存储Json文件
     *
     * @param json     json字符串
     * @param fileName 存储的文件名
     */
    public static void writeJson(String json,String fileName) {
        String cacheRoot = Environment.getExternalStorageDirectory().getAbsolutePath() + "/LDM/json/";
        File file = new File(cacheRoot);
        if (!file.exists()) {
            file.mkdirs();
        }
        String formatJson = JsonFormatUtils.format(json);
        try {
            File cacheFile = new File(cacheRoot, fileName);
            bw = new BufferedWriter(new FileWriter(cacheFile));
            bw.newLine();
            bw.write(formatJson);
            Log.e("storeJson", "保存数据到本地文件夹中:" + cacheFile);
            bw.close();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bw = null;
        }

    }

    /**
     * 读取json数据
     * @param fileName
     * @return 返回值为list
     */
    public static String readJson(String fileName) {
        String cacheRoot = Environment.getExternalStorageDirectory().getAbsolutePath() + "/LDM/json/";
        File file = new File(cacheRoot);
        if (!file.exists()) {
            file.mkdirs();
        }
        File cacheFile = new File(cacheRoot, fileName);
        StringBuffer stringBuffer = new StringBuffer();
        try {
            br = new BufferedReader(new FileReader(cacheFile));
            while (br.ready()) {
                stringBuffer.append(br.readLine().trim());
            }
            br.close();
            return stringBuffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            br = null;
        }
        return null;
    }
}