本框架目前還在迭代階段，并不適合于直接用于項目，只是我用來學(xué)習(xí)的小東西,源碼地址:https://github.com/xiangmingzhe/PictureCache
　在Android開發(fā)中，如果圖片過多，而我們又沒有對圖片進行有效的緩存，就很容易導(dǎo)致OOM（Out Of Memory）錯誤。因此，圖片的緩存是非常重要的，尤其是對圖片非常多的應(yīng)用。現(xiàn)在很多框架都做了很好的圖片緩存處理，如【Fresco】、【Glide】等。

1.說一下三級緩存的流程：

當我們的APP中想要加載某張圖片時，先去LruCache中尋找圖片，如果LruCache中有，則直接取出來使用，如果LruCache中沒有，則去SoftReference中尋找，如果SoftReference中有，則從SoftReference中取出圖片使用，同時將圖片重新放回到LruCache中，如果SoftReference中也沒有圖片，則去文件系統(tǒng)中尋找，如果有則取出來使用，同時將圖片添加到LruCache中，如果沒有，則連接網(wǎng)絡(luò)從網(wǎng)上下載圖片。圖片下載完成后，將圖片保存到文件系統(tǒng)中，然后放到LruCache中。

2.實現(xiàn)：

（1）網(wǎng)絡(luò)訪問工具類NetCache：

package com.picture.lib_rhythm.cache;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.text.TextUtils;
import android.util.Log;
import android.widget.ImageView;

import com.picture.lib_rhythm.R;
import com.picture.lib_rhythm.RequestCreator;
import com.picture.lib_rhythm.bean.TagInfo;
import com.picture.lib_rhythm.utils.BitmapUtils;
import com.picture.lib_rhythm.widgets.gif.GifImageView;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Iterator;
import java.util.Map;

/**
 * Time:2019/11/7
 * Author:xmz-dell
 * Description:網(wǎng)絡(luò)緩存類
 */
public class NetCache {
    private LruCache lruCache;
    private LocalCache localCache;
    private static final String TAG="NetCache";
    private Drawable errorDrawable;
    private Context mContext;
    private float radius=0f;
    public BitmapTask bitmapTask;
    public NetCache(Cache lruCache,LocalCache localCache){
        this.lruCache=(LruCache) lruCache;
        this.localCache=localCache;
    }
    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Object[] objects = (Object[]) msg.obj;
            ImageView imageView = (ImageView) objects[0];
            String mUrl = (String) objects[1];
            imageView.setTag(mUrl);
            setErrorView(objects,imageView);
        }
    };

    /**
     * 錯誤視圖
     * @param errorDrawable
     * @return
     */
    public NetCache error(Drawable errorDrawable){
        this.errorDrawable=errorDrawable;
        return this;
    }
    /**
     * 設(shè)置圓角
     * @param radius 弧度
     * @return
     */
    public NetCache transform(float radius) {
        this.radius=radius;
        return this;
    }

    /**
     * 是否需要設(shè)置圓角
     * @return
     */
    private boolean isRoundCorner(){
      return radius!=0f?true:false;
    }
    /**
     * 設(shè)置錯誤視圖
     * @param objects
     * @param imageView
     */
    private void setErrorView(Object[] objects,ImageView imageView){
        if(errorDrawable!=null){
            boolean isSuccess=(boolean) objects[2];
            if(!isSuccess){
                if(isRoundCorner()){
                    Bitmap bitmap=BitmapUtils.toRoundCorner(errorDrawable,radius,0);
                    imageView.setImageBitmap(bitmap);
                }else{
                    imageView.setImageDrawable(errorDrawable);
                }
            }
        }
    }
    /**
     * 加載圖片
     * @param iv
     * @param url
     */
    public void loadBitmap(final ImageView iv, final String url, Context context){
        if(iv==null||TextUtils.isEmpty(url)||context==null){
            throw new NullPointerException("ImageView Can not be empty || url Can not be empty || context Can not be empty");
        }
        this.mContext=context;
        new Handler().post(new Runnable() {
            @Override
            public void run() {
                Bitmap bitmap=loadBitmap(url);
                if(bitmap!=null){
                    sendBitmap(bitmap);
                }else{
                    bitmapTask=new BitmapTask();
                    pushTaskToMap(url,bitmapTask);
                    bitmapTask.execute(iv, url);// 啟動AsyncTask,
                }
            }
        });
    }

    /**
     * 將所有異步任務(wù)存儲
     * @param url
     * @param bitmapTask
     */
    private void pushTaskToMap(String url,BitmapTask bitmapTask){
        RequestCreator.getInstance().taskMap.put(url,bitmapTask);
    }
    /**
     * 取消單個請求
     */
    public void cancleTask(String tag){
        Map<String,NetCache.BitmapTask>taskMap= RequestCreator.getInstance().taskMap;
        Iterator<String> iterator =taskMap.keySet().iterator();// map中key（鍵）的迭代器對象
        while (iterator.hasNext()){// 循環(huán)取鍵值進行判斷
            String key = iterator.next();// 鍵
            if(tag.equals(key)){
                BitmapTask bitmapTask = taskMap.get(key);
                if(bitmapTask!=null){
                    bitmapTask.cancel(true);
                    iterator.remove();
                    break;
                }
            }
        }
    }

    /**
     * 取消全部請求
     */
    public void cancleAllTask(){
        Map<String,NetCache.BitmapTask>taskMap= RequestCreator.getInstance().taskMap;
        Iterator<String> iterator =taskMap.keySet().iterator();// map中key（鍵）的迭代器對象
        while (iterator.hasNext()){// 循環(huán)取鍵值進行判斷
            String key = iterator.next();// 鍵
                BitmapTask bitmapTask = taskMap.get(key);
                if(bitmapTask!=null){
                    bitmapTask.cancel(true);
                    iterator.remove();
                }

        }
    }

    /**
     * 嘗試下加載內(nèi)存-->磁盤
     * @param url
     * @return
     */
    private Bitmap loadBitmap(String url){
        if(lruCache.get(url)!=null){
                return lruCache.get(url);
        }
        if(localCache.getBitmapFromLocal(url)!=null){
            return localCache.getBitmapFromLocal(url);
        }
        return null;
    }


    /**
     * Handler和線程池的封裝
     * <p/>
     * 第一個泛型: 參數(shù)類型
     * 第二個泛型: 更新進度的泛型,
     * 第三個泛型是onPostExecute的返回結(jié)果
     */
    public class BitmapTask extends AsyncTask<Object, Void, Bitmap> {

        private ImageView ivPicture;
        private String url;
        private Object[] objects;
        private Message message;

        /**
         * 后臺耗時方法在此執(zhí)行, 子線程
         */
        @Override
        protected Bitmap doInBackground(Object... params) {
            ivPicture = (ImageView) params[0];
            url = (String) params[1];
            message = handler.obtainMessage();
            objects = new Object[]{ivPicture, url,true
            };
            message.obj = objects;
            handler.sendMessage(message);
            return downloadBitmap(url,ivPicture,objects,message);
        }

        /**
         * 更新進度, 主線程
         */
        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }

        /**
         * 耗時方法結(jié)束后,執(zhí)行該方法, 主線程
         */
        @Override
        protected void onPostExecute(Bitmap result) {
            if (result != null) {
                String bindUrl = (String) ivPicture.getTag();
                if (url.equals(bindUrl)) {// 確保圖片設(shè)定給了正確的imageview
                    sendBitmap(result);
                    localCache.setBitmapToLocal(url, result);// 將圖片保存在本地
                    lruCache.set(url, result);// 將圖片保存在內(nèi)存
                    Log.d(TAG,"從網(wǎng)絡(luò)緩存讀取圖片啦");
                }
            }else{
                Log.d(TAG,"圖片網(wǎng)絡(luò)加載失敗");
                message = handler.obtainMessage();
                objects = new Object[]{ivPicture, url,false
                };
                message.obj = objects;
                handler.sendMessage(message);

            }
        }
    }

    /**
     * 下載圖片
     *
     * @param url
     * @return
     */
    private Bitmap downloadBitmap(String url,ImageView iv,Object[]objects,Message message) {

        HttpURLConnection conn = null;
        try {
            conn = (HttpURLConnection) new URL(url).openConnection();
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            conn.connect();

            int responseCode = conn.getResponseCode();
            if (responseCode == 200) {
                InputStream inputStream = conn.getInputStream();

                //圖片壓縮處理
                BitmapFactory.Options option = new BitmapFactory.Options();
                // option.inSampleSize = 2;//寬高都壓縮為原來的二分之一, 此參數(shù)需要根據(jù)圖片要展示的大小來確定
                option.inPreferredConfig = Bitmap.Config.RGB_565;//設(shè)置圖片格式

                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, option);
                return bitmap;
            }

        } catch (Exception e) {
            Log.d(TAG,"圖片加載失敗,準備加載錯誤視圖");
            message = handler.obtainMessage();
            objects = new Object[]{iv, url,false
            };
            message.obj = objects;
            handler.sendMessage(message);
            e.printStackTrace();

        } finally {
            if (conn != null) {
                conn.disconnect();
            }
        }

        return null;
    }

    /**
     * 發(fā)送一個bitmap給上游
     * 下一個版本要替換成自定義rxandroid來實現(xiàn)。
     *
     */
    private void sendBitmap(Bitmap bitmap){
        if(onLoadSuccessListener!=null){
            onLoadSuccessListener.loadBitmapSuccess(bitmap);
        }
    }
    public OnLoadSuccessListener onLoadSuccessListener;
    public NetCache setOnLoadSuccessListener(OnLoadSuccessListener onLoadSuccessListener) {
        this.onLoadSuccessListener = onLoadSuccessListener;
        return this;
    }

    public interface OnLoadSuccessListener{
        void loadBitmapSuccess(Bitmap bitmap);
    }
}

（2）本地文件訪問類LocalCache ：

package com.picture.lib_rhythm.cache;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.text.TextUtils;
import android.util.Log;

import com.picture.lib_rhythm.utils.Utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Time:2019/11/7
 * Author:xmz-dell
 * Description:本地文件
 * */
public class LocalCache {
    private String cachePath;

    public LocalCache(Context context, String uniqueName) {
        if(TextUtils.isEmpty(uniqueName)){
            throw new NullPointerException("uniqueName Can not be empty");
        }
        cachePath = getCacheDirString(context, uniqueName);
    }

    /**
     * 根據(jù)url獲取bitmap
     * @param url
     * @return
     */
    public Bitmap getBitmapFromLocal(String url){
        try{
            File file = new File(cachePath, encode(url));
            if (file.exists()) {
                // 如果文件存在
                Bitmap bitmap = BitmapFactory.decodeStream(new FileInputStream(file));
                return bitmap;
            }
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 獲取緩存目錄的路徑
     * @param context
     * @param uniqueName
     * @return
     */
    private String getCacheDirString(Context context, String uniqueName) {
        File file = null;
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
                || !Environment.isExternalStorageRemovable()) {
            file = new File(context.getExternalCacheDir(), uniqueName);
        } else {
            file = new File(context.getCacheDir(), uniqueName);
        }
        if (!file.exists()) {
            file.mkdirs();
        }
        return file.getAbsolutePath();
    }

    /**
     * 設(shè)置Bitmap數(shù)據(jù)到本地
     *
     * @param url
     * @param bitmap
     */
    public void setBitmapToLocal(String url, Bitmap bitmap) {
        if(TextUtils.isEmpty(url)||bitmap==null){
            throw new NullPointerException("url Can not be empty || bitmap Can not be empty");
        }
        if(Utils.calculateSdCardCacheSize()<Utils.getBitmapKB(bitmap)){
            throw new IllegalArgumentException("sdcard Insufficient space left");
        }
        FileOutputStream fos = null;
        try {
            String fileName = encode(url);
            File file = new File(cachePath, fileName);
            File parentFile = file.getParentFile();//獲取上級所有目錄
            if (!parentFile.exists()) {
                // 如果文件不存在，則創(chuàng)建文件夾
                parentFile.mkdirs();
            }
            Log.d("保存的地址:","file.getAbsolutePath():"+file.getAbsolutePath());
            fos = new FileOutputStream(file);
            // 將圖片壓縮到本地
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (fos != null) {
                try {
                    fos.close();//關(guān)閉流
                    fos = null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }


    /***
     * md5 加密
     * @param pwd
     * @return
     */
    public  String encode(String pwd) {
        StringBuffer sb = new StringBuffer();
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            byte[] bytes = digest.digest(pwd.getBytes("UTF-8"));
            for (int i = 0; i < bytes.length; i++) {
                String s = Integer.toHexString(0xff & bytes[i]);

                if (s.length() == 1) {
                    sb.append("0" + s);
                } else {
                    sb.append(s);
                }
            }
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return sb.toString();
    }


}

（3）內(nèi)存工具類LruCache ：

package com.picture.lib_rhythm.cache;

import android.content.Context;
import android.graphics.Bitmap;
import android.text.TextUtils;

import com.picture.lib_rhythm.utils.Utils;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Time:2019/11/7
 * Author:xmz-dell
 * Description:
 */
public class LruCache implements Cache{
    private int size;
    private int maxSize;
    private int cacheCount; //緩存計數(shù)
    private int evictionCount;//清除計數(shù)
    private final LinkedHashMap<String, Bitmap> map; 

    public LruCache(Context context){
        this(Utils.calculateMemoryCacheSize(context));
    }
    public LruCache(int maxSize){
        if(maxSize<=0){
            throw new IllegalArgumentException("Max size Cannot be less than or equal to 0");
        }
        this.maxSize=maxSize;
        this.map = new LinkedHashMap<String, Bitmap>(0, 0.75f, true);
    }

    @Override
    public Bitmap get(String key) {
        if(TextUtils.isEmpty(key)){
            throw new NullPointerException("key Can not be empty");
        }
        synchronized (this){
            Bitmap bitmap;
            bitmap=map.get(key);
            if(bitmap!=null){
                cacheCount++;
                return bitmap;
            }
        }
        return null;
    }

    @Override
    public void set(String key, Bitmap bitmap) {
        if(TextUtils.isEmpty(key)||bitmap==null){
            throw new NullPointerException("key Can not be empty||bitmap Can not be empty");
        }
        Bitmap readyMoveBitmap;//等待移動的bitmap
        size+= Utils.getBitmapBytes(bitmap);//得到當前bitmap大小并疊加
        readyMoveBitmap=map.put(key,bitmap);
        if(readyMoveBitmap!=null){
            size-=Utils.getBitmapBytes(readyMoveBitmap);
        }

        reduceMemoryPressure();
    }

    /**
     * //如果當前size超過maxsize 就從前往后移除bitmap 來減少內(nèi)存
     */
    public void reduceMemoryPressure(){
        while(true){
            String key;
            Bitmap bitmap;
            synchronized (this){
                if(size<0||map.isEmpty()){
                    throw new NullPointerException("size Cannot be less than 0 ||map Can not be empty");
                }
                if(size<=maxSize||map.isEmpty()){//如果沒有超過閾值就結(jié)束整個死循環(huán);
                    break;
                }
                Map.Entry<String, Bitmap> decompose = map.entrySet().iterator().next();
                key=decompose.getKey();
                bitmap=decompose.getValue();
                map.remove(key);
                size-=Utils.getBitmapBytes(bitmap);
                evictionCount++;
            }
        }
    }
    @Override
    public int size() {
        return size;
    }

    @Override
    public int maxSize() {
        return maxSize;
    }

    @Override
    public void clear() {
        reduceMemoryPressure();
    }

    @Override
    public void clearKeyUri(String keyPrefix) {

    }
}

目前已經(jīng)實現(xiàn)的功能如下圖:

IMG20191125142151.jpg

最后調(diào)用方式如下

## 設(shè)置圖片四周圓角:
 Rhythm.with(context).load(url).transform(10.0f).into(imageView);
## 設(shè)置占位圖: 
Rhythm.with(context).load(url).placeholder(R.drawable.xx).into(imageView);
## 加載錯誤視圖:
 Rhythm.with(context).load(url).error(R.drawable.xx).into(imageView);
## 開啟加載gif圖片(正在優(yōu)化)
 Rhythm.with(context).load(url).openGif(false).into(imageView);
## 設(shè)置成圓形圖片
 Rhythm.with(context).load(url).style(TypeEnum.CIRCLE).into(imageView);
## 設(shè)置圓形or圓角圖片邊框
 Rhythm.with(context).load(url).style(TypeEnum.CIRCLE).boarder(2).into(imageView);
 
 Rhythm.with(context).load(url).transform(10.0f).boarder(2).into(imageView);
## 增加圖片漸變

## 圖片懶加載

## 取消單個加載
 Rhythm.with(ListActivity.this).cancleTask(tag);
## 取消所有加載
 Rhythm.with(context).cancleAllTask();

## 加載圖片高斯模糊效果
 Rhythm.with(context).bitmapTransform(new BlurTransformation(10)).into(imageView);
 其中BlurTransformation中分別包括模糊半徑和指定模糊前縮小的倍數(shù)。


# 動畫相關(guān)
### 圖片淡入淡出效果
 Rhythm.with(context).load(url).crossFade().into(imageView);
### 支持圖片自定義動畫
Rhythm.with(context).load(url).Animation(R.anim.xx).into(imageView);
### 設(shè)置無動畫
Rhythm.with(context).load(url).dontAnimation().into(imageView);
# 增加圖片水印功能,詳細功能:分為居中,左上角,右上角,左下角,右下角
### (1)居中水印
Rhythm.with(context).load(url).watermark(new WatermarkInfo(Watermark.CENTER,watermakeBitmap)).into(imageView);
### (2)左上角水印
 Rhythm.with(context).load(url)
                     .watermark(new WatermarkInfo(Watermark.LEFT_TOP,watermakeBitmap,paddingLeft,paddingTop,paddingRight,paddingBottom))
                     .into(imageView);
### (3)右上角水印                    
 Rhythm.with(context).load(url)
                    .watermark(new WatermarkInfo(Watermark.RIGHT_TOP,watermakeBitmap,paddingLeft,paddingTop,paddingRight,paddingBottom))
                     .into(imageView);
### (4)左下角水印                    
 Rhythm.with(context).load(url)
                  .watermark(new WatermarkInfo(Watermark.LEFT_BOTTOM,watermakeBitmap,paddingLeft,paddingTop,paddingRight,paddingBottom))
                     .into(imageView);                     
### (5)右下角水印                    
 Rhythm.with(context).load(url)
                .watermark(new WatermarkInfo(Watermark.RIGHT_BOTTOM,watermakeBitmap,paddingLeft,paddingTop,paddingRight,paddingBottom))
                     .into(imageView);