摘要：安卓開發一般都需要進行數據緩存，常用操作老司機已為你封裝完畢，經常有小伙伴問怎么判斷緩存是否可用，那我告訴你，你可以用這份工具進行存儲和查詢，具體可以查看源碼，現在為你開車，傳送門。

安卓開發一般都需要進行數據緩存，常用操作老司機已為你封裝完畢，經常有小伙伴問怎么判斷緩存是否可用，那我告訴你，你可以用這份工具進行存儲和查詢，具體可以查看源碼，現在為你開車，Demo傳送門。

put : 保存String數據到緩存中
getAsString : 讀取String數據
getAsJSONObject : 讀取JSONObject數據
getAsJSONArray : 讀取JSONArray數據
getAsBinary : 獲取byte數據
getAsObject : 讀取Serializable數據
getAsBitmap : 讀取bitmap數據
getAsDrawable : 讀取Drawable數據
file : 獲取緩存文件
remove : 除某個key
clear : 清除所有數據

public class AppACache {

// 用法例子
// ACache mCache = ACache.get(this); // 初始化，一般放在基類里
// mCache.put("test_key1","test value");
// mCache.put("test_key2", "test value", 10);// 保存10秒，如果超過10秒去獲取這個key，將為null
// mCache.put("test_key3", "test value", 2 ACache.TIME_DAY);// 保存兩天，如果超過兩天去獲取這個key，將為null
// String value = mCache.getAsString("test_key1");// 獲取數據

public static final int TIME_HOUR = 60 * 60;
public static final int TIME_DAY = TIME_HOUR * 24;
private static final int MAX_SIZE = 1000 * 1000 * 50; // 50 mb
private static final int MAX_COUNT = Integer.MAX_VALUE; // 不限制存放數據的數量
private static Map mInstanceMap = new HashMap();
private ACacheManager mCache;

public static AppACache get(Context ctx) {
    return get(ctx, "ACache");
}

public static AppACache get(Context ctx, String cacheName) {
    File f = new File(ctx.getCacheDir(), cacheName);
    return get(f, MAX_SIZE, MAX_COUNT);
}

public static AppACache get(File cacheDir) {
    return get(cacheDir, MAX_SIZE, MAX_COUNT);
}

public static AppACache get(Context ctx, long max_zise, int max_count) {
    File f = new File(ctx.getCacheDir(), "ACache");
    return get(f, max_zise, max_count);
}

public static AppACache get(File cacheDir, long max_zise, int max_count) {
    AppACache manager = mInstanceMap.get(cacheDir.getAbsoluteFile() + myPid());
    if (manager == null) {
        manager = new AppACache(cacheDir, max_zise, max_count);
        mInstanceMap.put(cacheDir.getAbsolutePath() + myPid(), manager);
    }
    return manager;
}

private static String myPid() {
    return "_" + android.os.Process.myPid();
}

private AppACache(File cacheDir, long max_size, int max_count) {
    if (!cacheDir.exists() && !cacheDir.mkdirs()) {
        throw new RuntimeException("can"t make dirs in "
                + cacheDir.getAbsolutePath());
    }
    mCache = new ACacheManager(cacheDir, max_size, max_count);
}

/**
 * Provides a means to save a cached file before the data are available.
 * Since writing about the file is complete, and its close method is called,
 * its contents will be registered in the cache. Example of use:
 *
 * ACache cache = new ACache(this) try { OutputStream stream =
 * cache.put("myFileName") stream.write("some bytes".getBytes()); // now
 * update cache! stream.close(); } catch(FileNotFoundException e){
 * e.printStackTrace() }
 */
class xFileOutputStream extends FileOutputStream {
    File file;

    public xFileOutputStream(File file) throws FileNotFoundException {
        super(file);
        this.file = file;
    }

    public void close() throws IOException {
        super.close();
        mCache.put(file);
    }
}

// =======================================
// ============ String數據 讀寫 ==============
// =======================================
/**
 * 保存 String數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的String數據
 */
public void put(String key, String value) {
    File file = mCache.newFile(key);
    BufferedWriter out = null;
    try {
        out = new BufferedWriter(new FileWriter(file), 1024);
        out.write(value);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (out != null) {
            try {
                out.flush();
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        mCache.put(file);
    }
}

/**
 * 保存 String數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的String數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, String value, int saveTime) {
    put(key, Utils.newStringWithDateInfo(saveTime, value));
}

/**
 * 讀取 String數據
 * 
 * @param key
 * @return String 數據
 */
public String getAsString(String key) {
    File file = mCache.get(key);
    if (!file.exists())
        return null;
    boolean removeFile = false;
    BufferedReader in = null;
    try {
        in = new BufferedReader(new FileReader(file));
        String readString = "";
        String currentLine;
        while ((currentLine = in.readLine()) != null) {
            readString += currentLine;
        }
        if (!Utils.isDue(readString)) {
            return Utils.clearDateInfo(readString);
        } else {
            removeFile = true;
            return null;
        }
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    } finally {
        if (in != null) {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (removeFile)
            remove(key);
    }
}

// =======================================
// ============= JSONObject 數據 讀寫 ==============
// =======================================
/**
 * 保存 JSONObject數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的JSON數據
 */
public void put(String key, JSONObject value) {
    put(key, value.toString());
}

/**
 * 保存 JSONObject數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的JSONObject數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, JSONObject value, int saveTime) {
    put(key, value.toString(), saveTime);
}

/**
 * 讀取JSONObject數據
 * 
 * @param key
 * @return JSONObject數據
 */
public JSONObject getAsJSONObject(String key) {
    String JSONString = getAsString(key);
    try {
        JSONObject obj = new JSONObject(JSONString);
        return obj;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

// =======================================
// ============ JSONArray 數據 讀寫 =============
// =======================================
/**
 * 保存 JSONArray數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的JSONArray數據
 */
public void put(String key, JSONArray value) {
    put(key, value.toString());
}

/**
 * 保存 JSONArray數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的JSONArray數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, JSONArray value, int saveTime) {
    put(key, value.toString(), saveTime);
}

/**
 * 讀取JSONArray數據
 * 
 * @param key
 * @return JSONArray數據
 */
public JSONArray getAsJSONArray(String key) {
    String JSONString = getAsString(key);
    try {
        JSONArray obj = new JSONArray(JSONString);
        return obj;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

// =======================================
// ============== byte 數據 讀寫 =============
// =======================================
/**
 * 保存 byte數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的數據
 */
public void put(String key, byte[] value) {
    File file = mCache.newFile(key);
    FileOutputStream out = null;
    try {
        out = new FileOutputStream(file);
        out.write(value);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (out != null) {
            try {
                out.flush();
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        mCache.put(file);
    }
}

/**
 * Cache for a stream
 *
 * @param key
 *            the file name.
 * @return OutputStream stream for writing data.
 * @throws FileNotFoundException
 *             if the file can not be created.
 */
public OutputStream put(String key) throws FileNotFoundException {
    return new xFileOutputStream(mCache.newFile(key));
}

/**
 *
 * @param key
 *            the file name.
 * @return (InputStream or null) stream previously saved in cache.
 * @throws FileNotFoundException
 *             if the file can not be opened
 */
public InputStream get(String key) throws FileNotFoundException {
    File file = mCache.get(key);
    if (!file.exists())
        return null;
    return new FileInputStream(file);
}

/**
 * 保存 byte數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, byte[] value, int saveTime) {
    put(key, Utils.newByteArrayWithDateInfo(saveTime, value));
}

/**
 * 獲取 byte 數據
 * 
 * @param key
 * @return byte 數據
 */
public byte[] getAsBinary(String key) {
    RandomAccessFile RAFile = null;
    boolean removeFile = false;
    try {
        File file = mCache.get(key);
        if (!file.exists())
            return null;
        RAFile = new RandomAccessFile(file, "r");
        byte[] byteArray = new byte[(int) RAFile.length()];
        RAFile.read(byteArray);
        if (!Utils.isDue(byteArray)) {
            return Utils.clearDateInfo(byteArray);
        } else {
            removeFile = true;
            return null;
        }
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    } finally {
        if (RAFile != null) {
            try {
                RAFile.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (removeFile)
            remove(key);
    }
}

// =======================================
// ============= 序列化 數據 讀寫 ===============
// =======================================
/**
 * 保存 Serializable數據 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的value
 */
public void put(String key, Serializable value) {
    put(key, value, -1);
}

/**
 * 保存 Serializable數據到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的value
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, Serializable value, int saveTime) {
    ByteArrayOutputStream baos = null;
    ObjectOutputStream oos = null;
    try {
        baos = new ByteArrayOutputStream();
        oos = new ObjectOutputStream(baos);
        oos.writeObject(value);
        byte[] data = baos.toByteArray();
        if (saveTime != -1) {
            put(key, data, saveTime);
        } else {
            put(key, data);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            oos.close();
        } catch (IOException e) {
        }
    }
}

/**
 * 讀取 Serializable數據
 * 
 * @param key
 * @return Serializable 數據
 */
public Object getAsObject(String key) {
    byte[] data = getAsBinary(key);
    if (data != null) {
        ByteArrayInputStream bais = null;
        ObjectInputStream ois = null;
        try {
            bais = new ByteArrayInputStream(data);
            ois = new ObjectInputStream(bais);
            Object reObject = ois.readObject();
            return reObject;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            try {
                if (bais != null)
                    bais.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if (ois != null)
                    ois.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return null;

}

// =======================================
// ============== bitmap 數據 讀寫 =============
// =======================================
/**
 * 保存 bitmap 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的bitmap數據
 */
public void put(String key, Bitmap value) {
    put(key, Utils.Bitmap2Bytes(value));
}

/**
 * 保存 bitmap 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的 bitmap 數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, Bitmap value, int saveTime) {
    put(key, Utils.Bitmap2Bytes(value), saveTime);
}

/**
 * 讀取 bitmap 數據
 * 
 * @param key
 * @return bitmap 數據
 */
public Bitmap getAsBitmap(String key) {
    if (getAsBinary(key) == null) {
        return null;
    }
    return Utils.Bytes2Bimap(getAsBinary(key));
}

// =======================================
// ============= drawable 數據 讀寫 =============
// =======================================
/**
 * 保存 drawable 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的drawable數據
 */
public void put(String key, Drawable value) {
    put(key, Utils.drawable2Bitmap(value));
}

/**
 * 保存 drawable 到 緩存中
 * 
 * @param key
 *            保存的key
 * @param value
 *            保存的 drawable 數據
 * @param saveTime
 *            保存的時間，單位：秒
 */
public void put(String key, Drawable value, int saveTime) {
    put(key, Utils.drawable2Bitmap(value), saveTime);
}

/**
 * 讀取 Drawable 數據
 * 
 * @param key
 * @return Drawable 數據
 */
public Drawable getAsDrawable(String key) {
    if (getAsBinary(key) == null) {
        return null;
    }
    return Utils.bitmap2Drawable(Utils.Bytes2Bimap(getAsBinary(key)));
}

/**
 * 獲取緩存文件
 * 
 * @param key
 * @return value 緩存的文件
 */
public File file(String key) {
    File f = mCache.newFile(key);
    if (f.exists())
        return f;
    return null;
}

/**
 * 移除某個key
 * 
 * @param key
 * @return 是否移除成功
 */
public boolean remove(String key) {
    return mCache.remove(key);
}

/**
 * 清除所有數據
 */
public void clear() {
    mCache.clear();
}

/**
 * @title 緩存管理器
 * @version 1.0
 */
public class ACacheManager {
    private final AtomicLong cacheSize;
    private final AtomicInteger cacheCount;
    private final long sizeLimit;
    private final int countLimit;
    private final Map lastUsageDates = Collections
            .synchronizedMap(new HashMap());
    protected File cacheDir;

    private ACacheManager(File cacheDir, long sizeLimit, int countLimit) {
        this.cacheDir = cacheDir;
        this.sizeLimit = sizeLimit;
        this.countLimit = countLimit;
        cacheSize = new AtomicLong();
        cacheCount = new AtomicInteger();
        calculateCacheSizeAndCacheCount();
    }

    /**
     * 計算 cacheSize和cacheCount
     */
    private void calculateCacheSizeAndCacheCount() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                int size = 0;
                int count = 0;
                File[] cachedFiles = cacheDir.listFiles();
                if (cachedFiles != null) {
                    for (File cachedFile : cachedFiles) {
                        size += calculateSize(cachedFile);
                        count += 1;
                        lastUsageDates.put(cachedFile,
                                cachedFile.lastModified());
                    }
                    cacheSize.set(size);
                    cacheCount.set(count);
                }
            }
        }).start();
    }

    private void put(File file) {
        int curCacheCount = cacheCount.get();
        while (curCacheCount + 1 > countLimit) {
            long freedSize = removeNext();
            cacheSize.addAndGet(-freedSize);

            curCacheCount = cacheCount.addAndGet(-1);
        }
        cacheCount.addAndGet(1);

        long valueSize = calculateSize(file);
        long curCacheSize = cacheSize.get();
        while (curCacheSize + valueSize > sizeLimit) {
            long freedSize = removeNext();
            curCacheSize = cacheSize.addAndGet(-freedSize);
        }
        cacheSize.addAndGet(valueSize);

        Long currentTime = System.currentTimeMillis();
        file.setLastModified(currentTime);
        lastUsageDates.put(file, currentTime);
    }

    private File get(String key) {
        File file = newFile(key);
        Long currentTime = System.currentTimeMillis();
        file.setLastModified(currentTime);
        lastUsageDates.put(file, currentTime);

        return file;
    }

    private File newFile(String key) {
        return new File(cacheDir, key.hashCode() + "");
    }

    private boolean remove(String key) {
        File image = get(key);
        return image.delete();
    }

    private void clear() {
        lastUsageDates.clear();
        cacheSize.set(0);
        File[] files = cacheDir.listFiles();
        if (files != null) {
            for (File f : files) {
                f.delete();
            }
        }
    }

    /**
     * 移除舊的文件
     * 
     * @return
     */
    private long removeNext() {
        if (lastUsageDates.isEmpty()) {
            return 0;
        }

        Long oldestUsage = null;
        File mostLongUsedFile = null;
        Set> entries = lastUsageDates.entrySet();
        synchronized (lastUsageDates) {
            for (Entry entry : entries) {
                if (mostLongUsedFile == null) {
                    mostLongUsedFile = entry.getKey();
                    oldestUsage = entry.getValue();
                } else {
                    Long lastValueUsage = entry.getValue();
                    if (lastValueUsage < oldestUsage) {
                        oldestUsage = lastValueUsage;
                        mostLongUsedFile = entry.getKey();
                    }
                }
            }
        }

        long fileSize = calculateSize(mostLongUsedFile);
        if (mostLongUsedFile.delete()) {
            lastUsageDates.remove(mostLongUsedFile);
        }
        return fileSize;
    }

    private long calculateSize(File file) {
        return file.length();
    }
}

/**
 * @title 時間計算工具類
 * @version 1.0
 */
private static class Utils {

    /**
     * 判斷緩存的String數據是否到期
     * 
     * @param str
     * @return true：到期了 false：還沒有到期
     */
    private static boolean isDue(String str) {
        return isDue(str.getBytes());
    }

    /**
     * 判斷緩存的byte數據是否到期
     * 
     * @param data
     * @return true：到期了 false：還沒有到期
     */
    private static boolean isDue(byte[] data) {
        String[] strs = getDateInfoFromDate(data);
        if (strs != null && strs.length == 2) {
            String saveTimeStr = strs[0];
            while (saveTimeStr.startsWith("0")) {
                saveTimeStr = saveTimeStr
                        .substring(1, saveTimeStr.length());
            }
            long saveTime = Long.valueOf(saveTimeStr);
            long deleteAfter = Long.valueOf(strs[1]);
            if (System.currentTimeMillis() > saveTime + deleteAfter * 1000) {
                return true;
            }
        }
        return false;
    }

    private static String newStringWithDateInfo(int second, String strInfo) {
        return createDateInfo(second) + strInfo;
    }

    private static byte[] newByteArrayWithDateInfo(int second, byte[] data2) {
        byte[] data1 = createDateInfo(second).getBytes();
        byte[] retdata = new byte[data1.length + data2.length];
        System.arraycopy(data1, 0, retdata, 0, data1.length);
        System.arraycopy(data2, 0, retdata, data1.length, data2.length);
        return retdata;
    }

    private static String clearDateInfo(String strInfo) {
        if (strInfo != null && hasDateInfo(strInfo.getBytes())) {
            strInfo = strInfo.substring(strInfo.indexOf(mSeparator) + 1,
                    strInfo.length());
        }
        return strInfo;
    }

    private static byte[] clearDateInfo(byte[] data) {
        if (hasDateInfo(data)) {
            return copyOfRange(data, indexOf(data, mSeparator) + 1,
                    data.length);
        }
        return data;
    }

    private static boolean hasDateInfo(byte[] data) {
        return data != null && data.length > 15 && data[13] == "-"
                && indexOf(data, mSeparator) > 14;
    }

    private static String[] getDateInfoFromDate(byte[] data) {
        if (hasDateInfo(data)) {
            String saveDate = new String(copyOfRange(data, 0, 13));
            String deleteAfter = new String(copyOfRange(data, 14,
                    indexOf(data, mSeparator)));
            return new String[] { saveDate, deleteAfter };
        }
        return null;
    }

    private static int indexOf(byte[] data, char c) {
        for (int i = 0; i < data.length; i++) {
            if (data[i] == c) {
                return i;
            }
        }
        return -1;
    }

    private static byte[] copyOfRange(byte[] original, int from, int to) {
        int newLength = to - from;
        if (newLength < 0)
            throw new IllegalArgumentException(from + " > " + to);
        byte[] copy = new byte[newLength];
        System.arraycopy(original, from, copy, 0,
                Math.min(original.length - from, newLength));
        return copy;
    }

    private static final char mSeparator = " ";

    private static String createDateInfo(int second) {
        String currentTime = System.currentTimeMillis() + "";
        while (currentTime.length() < 13) {
            currentTime = "0" + currentTime;
        }
        return currentTime + "-" + second + mSeparator;
    }

    /*
     * Bitmap → byte[]
     */
    private static byte[] Bitmap2Bytes(Bitmap bm) {
        if (bm == null) {
            return null;
        }
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
        return baos.toByteArray();
    }

    /*
     * byte[] → Bitmap
     */
    private static Bitmap Bytes2Bimap(byte[] b) {
        if (b.length == 0) {
            return null;
        }
        return BitmapFactory.decodeByteArray(b, 0, b.length);
    }

    /*
     * Drawable → Bitmap
     */
    private static Bitmap drawable2Bitmap(Drawable drawable) {
        if (drawable == null) {
            return null;
        }
        // 取 drawable 的長寬
        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();
        // 取 drawable 的顏色格式
        Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
                : Bitmap.Config.RGB_565;
        // 建立對應 bitmap
        Bitmap bitmap = Bitmap.createBitmap(w, h, config);
        // 建立對應 bitmap 的畫布
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, w, h);
        // 把 drawable 內容畫到畫布中
        drawable.draw(canvas);
        return bitmap;
    }

    /*
     * Bitmap → Drawable
     */
    @SuppressWarnings("deprecation")
    private static Drawable bitmap2Drawable(Bitmap bm) {
        if (bm == null) {
            return null;
        }
        return new BitmapDrawable(bm);
    }
}

}

好了，終點站到了，如果對本次旅途滿意的話，請給五星好評哦，沒關注的小伙伴輕輕點個上方的關注，畢竟老司機犧牲了很多時間才換來這么一份工具類，如果該工具類依賴其他工具類，都可以在我的史上最全的常用開發工具類收集（持續更新中）中找到。