Android简单实现 缓存数据

/**
 * Created by huangbo on 2017/6/19.
 *
 * 主要是缓存的工具类
 *
 * 缓存设计：
 *         0.从内存中读取数据 ：0.1 读取成功-> 取出versionCode ->3
 *                             0.2 读取失败-> 1
 *
 *         1.从文件中读取数据：1.1读取成成功-> 取出versionCode ->3
 *                             1.2读取失败-> 2
 *         2.从Assets中读取数据：2.1读取成功-> 取出versionCode ->3
 *                                2.2读取失败-> versionCode==0 ->3
 *
 *         3.用versionCode请求网络 3.1请求成功（有版本更新）将文件写入内存，写入文件；
 *                                 3.1 请求失败，（没有版本更新）
 *
 */

public class CacheData {

    public static CacheData cacheData;

    public static CacheData getInstance() {
        if (cacheData == null) {
            cacheData = new CacheData();
        }
        return cacheData;
    }

    String mFileName;

    public CacheData cacheName(String mFileName) {
        this.mFileName = mFileName;
        return this;
    }


    ExecutorService cachedThreadPool;

    private CacheData() {
        cachedThreadPool = Executors.newCachedThreadPool();
    }


    /**
     * 从assets 中读取文件
     *
     * @return cacheData 的Json串
     */
    private String readDataFromAssets() {
        try {
            InputStream ips = AppUtils.ApplicationContext.getAssets().open(mFileName);
            byte[] bytes = new byte[ips.available()];
            ips.read(bytes);
            ips.close();
            return new String(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "";
    }

    public void readDataFromAssets(final Handler handler) {
        cachedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                String json = readDataFromAssets();
                Message message = handler.obtainMessage(1, json);
                handler.sendMessage(message);
            }
        });
    }
    public void readDataFromFile(final Handler handler) {
        cachedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                Message message = handler.obtainMessage(1, readDataFromFile());
                handler.sendMessage(message);
            }
        });

    }

    /**
     * 将region 更新到指定文件里
     * @param
     */

    public void writeData2FileWithThread(final String Data) {
        cachedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                writeRegion2File(Data);
            }
        });
    }

    /**
     * @return cacheData 的Json串
     */

    private String readDataFromFile() {
        try {
            File file = new File(AppUtils.getCacheDirectory(), mFileName);
            if (!file.exists()) {
                return null;
            }
            FileInputStream fis = new FileInputStream(file);
            byte[] bytes = new byte[fis.available()];
            fis.read(bytes);
            fis.close();
            return new String(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "";

    }

    private void writeData2File(String jsonData) {
        try {
            File cityFile = new File(AppUtils.getCacheDirectory(), mFileName);
            if (!cityFile.exists()) {
                cityFile.createNewFile();
            }
            FileOutputStream fos = new FileOutputStream(cityFile);
            fos.write(regionJsonData.getBytes("UTF-8"));
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

/**
 * Created by huangbo on 2017/6/8.
 */

public class Region {
    public static Region region;

    public static Region getInstance() {
        if (region == null) {
            region = new Region();
        }
        return region;
    }


    ProvinceCityBean provinceCityBean;

    public int getVersion() {
        return provinceCityBean == null ? 0 : provinceCityBean.getVersion();
    }

    public ProvinceCityBean getProvinceCityBean() {
        return provinceCityBean;
    }

    public void setProvinceCityBean(final String mRegionJson, final Handler handler) {
        if (TextUtils.isEmpty(mRegionJson)) {
            return;
        }
        cachedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                provinceCityBean = GsonUtils.GsonToBean(mRegionJson, ProvinceCityBean.class);
                if (handler != null) {
                    handler.sendEmptyMessage(1);
                }
            }
        });
    }
    ExecutorService cachedThreadPool;
    CacheData cacheData;

    private Region() {
        cachedThreadPool = Executors.newCachedThreadPool();
        cacheData = CacheData.getInstance().cacheName(Const.REGION_JSON);
    }


    /**
     * 具体调用方法
     */
    public void cacheRegion() {
        if (provinceCityBean == null) {
            readRegionFromFile();
        } else {
            readRegionFromHttp();
        }
    }

    private void readRegionFromFile() {
        cacheData.readDataFromFile(new Handler() {
            @Override
            public void handleMessage(Message msg) {
                String jsonRegion = (String) msg.obj;
                onReadRegionFromFileBack(jsonRegion);
            }
        });
    }

    /**
     * 从文件中读取数据，若为null 继续从Asset中获取
     *
     * @param jsonRegion
     */
    private void onReadRegionFromFileBack(String jsonRegion) {
        if (!TextUtils.isEmpty(jsonRegion)) {/*文件中读取成功 设置到Region中更新json 取出version请求网络判断是否为最新的版本 */
            setProvinceCityBean(jsonRegion, httpHandler);
        } else {/*文件中读取失败  从assets 中继续读取*/
            cacheData.readDataFromAssets(new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    String jsonRegion = (String) msg.obj;
                    onReadRegionFromAssetsBack(jsonRegion);
                }
            });
        }
    }

    private void onReadRegionFromAssetsBack(String jsonRegion) {
        if (!TextUtils.isEmpty(jsonRegion)) {/*从assets中读取成功 设置到Region中更新json*/
            setProvinceCityBean(jsonRegion, httpHandler);
        } else {
            readRegionFromHttp();
        }
    }

    private void readRegionFromHttp() {
        ReqRegion reqRegion = new ReqRegion();
        reqRegion.sendRequest(false, new OnHttpResult() {
            @Override
            public void onHttpSuccess(String data) {
                setProvinceCityBean(data, null);
                cacheData.writeData2FileWithThread(data);
            }
            @Override
            public void onHttpFailure(String message) {

            }
        });
    }

    Handler httpHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            readRegionFromHttp();
        }
    };
}

Region.getInstance().cacheRegion();//实现缓存