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Android中Rxjava實(shí)現(xiàn)三級(jí)緩存的兩種方式

 更新時(shí)間：2017年04月07日 17:21:10   作者：我想要有你在的未來  
這篇文章主要介紹了Android中Rxjava實(shí)現(xiàn)三級(jí)緩存的兩種方式，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下。

本文正如標(biāo)題所說的用rxjava實(shí)現(xiàn)數(shù)據(jù)的三級(jí)緩存分別為內(nèi)存，磁盤，網(wǎng)絡(luò)，剛好最近在看Android源碼設(shè)計(jì)模式解析與實(shí)戰(zhàn)（受里面的ImageLoader的設(shè)計(jì)啟發(fā)）。

我把代碼放到了我的hot項(xiàng)目中，github地址

源碼下載地址：Rxjava_jb51.rar

1.使用concat()和first()的操作符。

2.使用BehaviorSubject。

先說BehaviorSubject的實(shí)現(xiàn)方法，廢話不多說直接上代碼，

/**
 * Created by wukewei on 16/6/20.
 */
public class BehaviorSubjectFragment extends BaseFragment {

  public static BehaviorSubjectFragment newInstance() {
    BehaviorSubjectFragment fragment = new BehaviorSubjectFragment();
    return fragment;
  }

  String diskData = null;
  String networkData = "從服務(wù)器獲取的數(shù)據(jù)";
  BehaviorSubject<String> cache;

  View mView;

  @Nullable
  @Override
  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    mView = inflater.inflate(R.layout.fragment_content, container, false);
    init();
    return mView;
  }

  private void init() {
    mView.findViewById(R.id.get).setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        subscriptionData(new Observer<String>() {
          @Override
          public void onCompleted() {

          }

          @Override
          public void onError(Throwable e) {

          }

          @Override
          public void onNext(String s) {
            Log.d("onNext", s);
          }
        });
      }
    });

    mView.findViewById(R.id.memory).setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        BehaviorSubjectFragment.this.cache = null;
      }
    });

    mView.findViewById(R.id.memory_disk).setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        BehaviorSubjectFragment.this.cache = null;
        BehaviorSubjectFragment.this.diskData = null;
      }
    });

  }

  private void loadNewWork() {
    Observable<String> o = Observable.just(networkData)
        .doOnNext(new Action1<String>() {
          @Override
          public void call(String s) {
            BehaviorSubjectFragment.this.diskData = s;
            Log.d("寫入磁盤", "寫入磁盤");
          }
        });
    o.subscribe(new Action1<String>() {
      @Override
      public void call(String s) {
        cache.onNext(s);
      }
    }, new Action1<Throwable>() {
      @Override
      public void call(Throwable throwable) {

      }
    });
  }

  private Subscription subscriptionData(@NonNull Observer<String> observer) {
    if (cache == null) {
      cache = BehaviorSubject.create();
      Observable.create(new Observable.OnSubscribe<String>() {
        @Override
        public void call(Subscriber<? super String> subscriber) {
          String data = diskData;
          if (data == null) {
            Log.d("來自網(wǎng)絡(luò)", "來自網(wǎng)絡(luò)");
            loadNewWork();
          } else {
            Log.d("來自磁盤", "來自磁盤");
            subscriber.onNext(data);
          }
        }
      })
          .subscribeOn(Schedulers.io())
          .subscribe(cache);

    } else {
      Log.d("來自內(nèi)存", "來自內(nèi)存");
    }

    return cache.observeOn(AndroidSchedulers.mainThread()).subscribe(observer);
  }


}

其中最主要的是subscriptionData（）這個(gè)方法，就是先判斷 cache是否存在要是存在的話就返回內(nèi)存中數(shù)據(jù)，再去判斷磁盤數(shù)據(jù)是否存在，如果存在就返回，要是前面兩種都不存在的時(shí)候，再去網(wǎng)絡(luò)中獲取數(shù)據(jù)。還有最重要的是當(dāng)你從網(wǎng)絡(luò)獲取數(shù)據(jù)的時(shí)候要記得保存在內(nèi)存中和保存在磁盤中，在磁盤獲取數(shù)據(jù)的時(shí)候把它賦值給內(nèi)存。

接下來就說說用concat()和first()的操作符來實(shí)現(xiàn)，這是我在看Android源碼設(shè)計(jì)模式解析與實(shí)戰(zhàn)，作者在第一章的時(shí)候就介紹ImageLoader的設(shè)計(jì)。

在內(nèi)存中存儲(chǔ)的方式LruCache來實(shí)現(xiàn)的，磁盤存儲(chǔ)的方式就是序列化存儲(chǔ)。

1.定義一個(gè)接口：

/**
 * Created by wukewei on 16/6/19.
 */
public interface ICache {
  <T> Observable<T> get(String key, Class<T> cls);

  <T> void put(String key, T t);
}

2.內(nèi)存存儲(chǔ)的實(shí)現(xiàn)

/**
 * Created by wukewei on 16/6/19.
 */
public class MemoryCache implements ICache{

  private LruCache<String, String> mCache;

  public MemoryCache() {
    final int maxMemory = (int) Runtime.getRuntime().maxMemory();
    final int cacheSize = maxMemory / 8;
    mCache = new LruCache<String, String>(cacheSize) {
      @Override
      protected int sizeOf(String key, String value) {
        try {
          return value.getBytes("UTF-8").length;
        } catch (UnsupportedEncodingException e) {
          e.printStackTrace();
          return value.getBytes().length;
        }
      }
    };
  }

  @Override
  public <T> Observable<T> get(final String key, final Class<T> cls) {
    return Observable.create(new Observable.OnSubscribe<T>() {
      @Override
      public void call(Subscriber<? super T> subscriber) {

        String result = mCache.get(key);

        if (subscriber.isUnsubscribed()) {
          return;
        }

        if (TextUtils.isEmpty(result)) {
          subscriber.onNext(null);
        } else {
          T t = new Gson().fromJson(result, cls);
          subscriber.onNext(t);
        }

        subscriber.onCompleted();
      }
    });
  }

  @Override
  public <T> void put(String key, T t) {
    if (null != t) {
      mCache.put(key, new Gson().toJson(t));
    }
  }

  public void clearMemory(String key) {
    mCache.remove(key);
  }
}

3.磁盤存儲(chǔ)的實(shí)現(xiàn)

/**
 * Created by wukewei on 16/6/19.
 */
public class DiskCache implements ICache{

  private static final String NAME = ".db";
  public static long OTHER_CACHE_TIME = 10 * 60 * 1000;
  public static long WIFI_CACHE_TIME = 30 * 60 * 1000;
  File fileDir;
  public DiskCache() {
    fileDir = CacheLoader.getApplication().getCacheDir();
  }

  @Override
  public <T> Observable<T> get(final String key, final Class<T> cls) {
    return Observable.create(new Observable.OnSubscribe<T>() {
      @Override
      public void call(Subscriber<? super T> subscriber) {

        T t = (T) getDiskData1(key + NAME);

        if (subscriber.isUnsubscribed()) {
          return;
        }

        if (t == null) {
          subscriber.onNext(null);
        } else {
          subscriber.onNext(t);
        }

        subscriber.onCompleted();
      }
    })
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread());

  }

  @Override
  public <T> void put(final String key, final T t) {
    Observable.create(new Observable.OnSubscribe<T>() {
      @Override
      public void call(Subscriber<? super T> subscriber) {

        boolean isSuccess = isSave(key + NAME, t);

        if (!subscriber.isUnsubscribed() && isSuccess) {

          subscriber.onNext(t);
          subscriber.onCompleted();
        }
      }
    })
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe();
  }

  /**
   * 保存數(shù)據(jù)
   */
  private <T> boolean isSave(String fileName, T t) {
    File file = new File(fileDir, fileName);

    ObjectOutputStream objectOut = null;
    boolean isSuccess = false;
    try {
      FileOutputStream out = new FileOutputStream(file);
          objectOut = new ObjectOutputStream(out);
      objectOut.writeObject(t);
      objectOut.flush();
      isSuccess=true;
    } catch (IOException e) {
      Log.e("寫入緩存錯(cuò)誤",e.getMessage());
    } catch (Exception e) {
      Log.e("寫入緩存錯(cuò)誤",e.getMessage());
    } finally {
      closeSilently(objectOut);
    }
    return isSuccess;
  }

  /**
   * 獲取保存的數(shù)據(jù)
   */
  private Object getDiskData1(String fileName) {
    File file = new File(fileDir, fileName);

    if (isCacheDataFailure(file)) {
      return null;
    }

    if (!file.exists()) {
      return null;
    }
    Object o = null;
    ObjectInputStream read = null;
    try {
      read = new ObjectInputStream(new FileInputStream(file));
      o = read.readObject();
    } catch (StreamCorruptedException e) {
      Log.e("讀取錯(cuò)誤", e.getMessage());
    } catch (IOException e) {
      Log.e("讀取錯(cuò)誤", e.getMessage());
    } catch (ClassNotFoundException e) {
      Log.e("錯(cuò)誤", e.getMessage());
    } finally {
      closeSilently(read);
    }
    return o;
  }



  private void closeSilently(Closeable closeable) {
    if (closeable != null) {
      try {
        closeable.close();
      } catch (Exception ignored) {
      }
    }
  }



  /**
   * 判斷緩存是否已經(jīng)失效
   */
  private boolean isCacheDataFailure(File dataFile) {
    if (!dataFile.exists()) {
      return false;
    }
    long existTime = System.currentTimeMillis() - dataFile.lastModified();
    boolean failure = false;
    if (NetWorkUtil.getNetworkType(CacheLoader.getApplication()) == NetWorkUtil.NETTYPE_WIFI) {
      failure = existTime > WIFI_CACHE_TIME ? true : false;
    } else {
      failure = existTime > OTHER_CACHE_TIME ? true : false;
    }

    return failure;
  }

  public void clearDisk(String key) {
    File file = new File(fileDir, key + NAME);
    if (file.exists()) file.delete();
  }
}

isCacheDataFailure（）方式中就是判斷當(dāng)前的數(shù)據(jù)是否失效，我是根據(jù)當(dāng)前的網(wǎng)絡(luò)狀況來分wifi狀況和非wifi狀況，wifi狀態(tài)下數(shù)據(jù)過期時(shí)間比較短，其他狀態(tài)過期時(shí)間比較長(zhǎng)。

4.CacheLoader的設(shè)計(jì)

/
**
 * Created by wukewei on 16/6/19.
 */
public class CacheLoader {
  private static Application application;

  public static Application getApplication() {
    return application;
  }

  private ICache mMemoryCache, mDiskCache;

  private CacheLoader() {

    mMemoryCache = new MemoryCache();
    mDiskCache = new DiskCache();
  }
  private static CacheLoader loader;

  public static CacheLoader getInstance(Context context) {
    application = (Application) context.getApplicationContext();
    if (loader == null) {
      synchronized (CacheLoader.class) {
        if (loader == null) {
          loader = new CacheLoader();
        }
      }
    }
    return loader;
  }


  public <T> Observable<T> asDataObservable(String key, Class<T> cls, NetworkCache<T> networkCache) {

    Observable observable = Observable.concat(
        memory(key, cls),
        disk(key, cls),
        network(key, cls, networkCache))
        .first(new Func1<T, Boolean>() {
          @Override
          public Boolean call(T t) {
            return t != null;
          }
        });
    return observable;
  }

  private <T> Observable<T> memory(String key, Class<T> cls) {

    return mMemoryCache.get(key, cls).doOnNext(new Action1<T>() {
      @Override
      public void call(T t) {
        if (null != t) {
          Log.d("我是來自內(nèi)存","我是來自內(nèi)存");
        }
      }
    });
  }

  private <T> Observable<T> disk(final String key, Class<T> cls) {

    return mDiskCache.get(key, cls)
        .doOnNext(new Action1<T>() {
          @Override
          public void call(T t) {
            if (null != t) {
              Log.d("我是來自磁盤","我是來自磁盤");
              mMemoryCache.put(key, t);
            }
          }
        });
  }

  private <T> Observable<T> network(final String key, Class<T> cls
      , NetworkCache<T> networkCache) {

    return networkCache.get(key, cls)
        .doOnNext(new Action1<T>() {
          @Override
          public void call(T t) {
            if (null != t) {
              Log.d("我是來自網(wǎng)絡(luò)","我是來自網(wǎng)絡(luò)");
              mDiskCache.put(key, t);
              mMemoryCache.put(key, t);
            }
          }
        });
  }


  public void clearMemory(String key) {
    ((MemoryCache)mMemoryCache).clearMemory(key);
  }



  public void clearMemoryDisk(String key) {
    ((MemoryCache)mMemoryCache).clearMemory(key);
    ((DiskCache)mDiskCache).clearDisk(key);
  }
}

5.網(wǎng)絡(luò)獲取的NetworkCache：

/**
 * Created by wukewei on 16/6/19.
 */
public abstract class NetworkCache<T> {
  public abstract Observable<T> get(String key, final Class<T> cls);
}

6.接下來看怎么使用

/**
 * Created by wukewei on 16/5/30.
 */
public class ItemPresenter extends BasePresenter<ItemContract.View> implements ItemContract.Presenter {

  private static final String key = "new_list";
  protected int pn = 1;

  protected void replacePn() {
    pn = 1;
  }

  private boolean isRefresh() {
    return pn == 1;
  }

  private NetworkCache<ListPopular> networkCache;


  public ItemPresenter(Activity activity, ItemContract.View view) {
    super(activity, view);

  }

  @Override
  public void getListData(String type) {
    if (isRefresh()) mView.showLoading();
    networkCache = new NetworkCache<ListPopular>() {
      @Override
      public Observable<ListPopular> get(String key, Class<ListPopular> cls) {
        return mHotApi.getPopular(ItemPresenter.this.pn, Constants.PAGE_SIZE, type)
            .compose(SchedulersCompat.applyIoSchedulers())
            .compose(RxResultHelper.handleResult())
            .flatMap(populars -> {
              ListPopular popular = new ListPopular(populars);
              return Observable.just(popular);
            });
      }
    };

    Subscription subscription = CacheLoader.getInstance(mActivity)
        .asDataObservable(key + type + ItemPresenter.this.pn, ListPopular.class, networkCache)
        .map(listPopular -> listPopular.data)
        .subscribe(populars -> {
          mView.showContent();
          if (isRefresh()) {
            if (populars.size() == 0) mView.showNotdata();
            mView.addRefreshData(populars);
          } else {
            mView.addLoadMoreData(populars);
          }
        }, throwable -> {
          if (isRefresh())
          mView.showError(ErrorHanding.handleError(throwable));
          handleError(throwable);
        });

    addSubscrebe(subscription);

  }
}

一定要給個(gè)key，我是根據(jù)key來獲取數(shù)據(jù)的，還要就是給個(gè)類型。

但是這個(gè)我設(shè)計(jì)的這個(gè)緩存還是不是很理想，接來下想要實(shí)現(xiàn)的就是在傳入的時(shí)候類的class都不用給明，要是有好的實(shí)現(xiàn)的方式，歡迎告訴我。

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