android lrucache使用
| 双击代码复制 | |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 | importjava.lang.reflect.Field; importjava.util.LinkedList; importjava.util.concurrent.ExecutorService; importjava.util.concurrent.Executors; importjava.util.concurrent.Semaphore;
importandroid.graphics.Bitmap; importandroid.graphics.BitmapFactory; importandroid.os.Handler; importandroid.os.Looper; importandroid.os.Message; importandroid.support.v4.util.LruCache; importandroid.util.DisplayMetrics; importandroid.view.ViewGroup.LayoutParams; importandroid.widget.ImageView;
publicclass ImageLoader { /** * 图片缓存的核心类 */ privateLruCache /** * 线程池 */ privateExecutorService mThreadPool; /** * 队列的调度方式 */ privateType mType = Type.LIFO; /** * 任务队列 */ privateLinkedList /** * 轮询的线程 */ privateThread mPoolThread; privateHandler mPoolThreadHander;
/** * 运行在UI线程的handler，用于给ImageView设置图片 */ privateHandler mHandler;
/** * 引入一个值为1的信号量，防止mPoolThreadHander未初始化完成 */ privatevolatile Semaphore mSemaphore = newSemaphore(0);
/** * 引入一个值为1的信号量，由于线程池内部也有一个阻塞线程，防止加入任务的速度过快，使LIFO效果不明显 */ privatevolatile Semaphore mPoolSemaphore;
privatestatic ImageLoader mInstance;
/** * 队列的调度方式 * * @author zhy * */ publicenum Type { FIFO, LIFO }
/** * 单例获得该实例对象 * * @return */ publicstatic ImageLoader getInstance() {
if(mInstance == null) { synchronized(ImageLoader.class) { if(mInstance == null) { mInstance = newImageLoader(1, Type.LIFO); } } } returnmInstance; }
privateImageLoader(intthreadCount, Type type) { init(threadCount, type); }
privatevoid init(intthreadCount, Type type) { // loop thread mPoolThread = newThread() { @Override publicvoid run() { Looper.prepare();
mPoolThreadHander = newHandler() { @Override publicvoid handleMessage(Message msg) { mThreadPool.execute(getTask()); try{ mPoolSemaphore.acquire(); }catch(InterruptedException e) { } } }; // 释放一个信号量 mSemaphore.release(); Looper.loop(); } }; mPoolThread.start();
// 获取应用程序最大可用内存 intmaxMemory = (int) Runtime.getRuntime().maxMemory(); intcacheSize = maxMemory / 8; mLruCache = newLruCache @Override protectedint sizeOf(String key, Bitmap value) { returnvalue.getRowBytes() * value.getHeight(); }; };
mThreadPool = Executors.newFixedThreadPool(threadCount); mPoolSemaphore = newSemaphore(threadCount); mTasks = newLinkedList mType = type == null? Type.LIFO : type;
}
/** * 加载图片 * * @param path * @param imageView */ publicvoid loadImage(finalString path, finalImageView imageView) { // set tag imageView.setTag(path); // UI线程 if(mHandler == null) { mHandler = newHandler() { @Override publicvoid handleMessage(Message msg) { ImgBeanHolder holder = (ImgBeanHolder) msg.obj; ImageView imageView = holder.imageView; Bitmap bm = holder.bitmap; String path = holder.path; if(imageView.getTag().toString().equals(path)) { imageView.setImageBitmap(bm); } } }; }
Bitmap bm = getBitmapFromLruCache(path); if(bm != null) { ImgBeanHolder holder = newImgBeanHolder(); holder.bitmap = bm; holder.imageView = imageView; holder.path = path; Message message = Message.obtain(); message.obj = holder; mHandler.sendMessage(message); }else{ addTask(newRunnable() { @Override publicvoid run() {
ImageSize imageSize = getImageViewWidth(imageView);
intreqWidth = imageSize.width; intreqHeight = imageSize.height;
Bitmap bm = decodeSampledBitmapFromResource(path, reqWidth, reqHeight); addBitmapToLruCache(path, bm); ImgBeanHolder holder = newImgBeanHolder(); holder.bitmap = getBitmapFromLruCache(path); holder.imageView = imageView; holder.path = path; Message message = Message.obtain(); message.obj = holder; // Log.e("TAG", "mHandler.sendMessage(message);"); mHandler.sendMessage(message); mPoolSemaphore.release(); } }); }
}
/** * 添加一个任务 * * @param runnable */ privatesynchronized void addTask(Runnable runnable) { try{ // 请求信号量，防止mPoolThreadHander为null if(mPoolThreadHander == null) mSemaphore.acquire(); }catch(InterruptedException e) { } mTasks.add(runnable);
mPoolThreadHander.sendEmptyMessage(0x110); }
/** * 取出一个任务 * * @return */ privatesynchronized Runnable getTask() { if(mType == Type.FIFO) { returnmTasks.removeFirst(); }elseif (mType == Type.LIFO) { returnmTasks.removeLast(); } returnnull; }
/** * 单例获得该实例对象 * * @return */ publicstatic ImageLoader getInstance(intthreadCount, Type type) {
if(mInstance == null) { synchronized(ImageLoader.class) { if(mInstance == null) { mInstance = newImageLoader(threadCount, type); } } } returnmInstance; }
/** * 根据ImageView获得适当的压缩的宽和高 * * @param imageView * @return */ privateImageSize getImageViewWidth(ImageView imageView) { ImageSize imageSize = newImageSize(); finalDisplayMetrics displayMetrics = imageView.getContext() .getResources().getDisplayMetrics(); finalLayoutParams params = imageView.getLayoutParams();
intwidth = params.width == LayoutParams.WRAP_CONTENT ? 0: imageView .getWidth();// Get actual image width if(width <= 0) width = params.width; // Get layout width parameter if(width <= 0) width = getImageViewFieldValue(imageView, "mMaxWidth");// Check // maxWidth // parameter if(width <= 0) width = displayMetrics.widthPixels; intheight = params.height == LayoutParams.WRAP_CONTENT ? 0: imageView .getHeight();// Get actual image height if(height <= 0) height = params.height; // Get layout height parameter if(height <= 0) height = getImageViewFieldValue(imageView, "mMaxHeight");// Check // maxHeight // parameter if(height <= 0) height = displayMetrics.heightPixels; imageSize.width = width; imageSize.height = height; returnimageSize;
}
/** * 从LruCache中获取一张图片，如果不存在就返回null。 */ privateBitmap getBitmapFromLruCache(String key) { returnmLruCache.get(key); }
/** * 往LruCache中添加一张图片 * * @param key * @param bitmap */ privatevoid addBitmapToLruCache(String key, Bitmap bitmap) { if(getBitmapFromLruCache(key) == null) { if(bitmap != null) mLruCache.put(key, bitmap); } }
/** * 计算inSampleSize，用于压缩图片 * * @param options * @param reqWidth * @param reqHeight * @return */ privateint calculateInSampleSize(BitmapFactory.Options options, intreqWidth, intreqHeight) { // 源图片的宽度 intwidth = options.outWidth; intheight = options.outHeight; intinSampleSize = 1;
if(width > reqWidth && height > reqHeight) { // 计算出实际宽度和目标宽度的比率 intwidthRatio = Math.round((float) width / (float) reqWidth); intheightRatio = Math.round((float) width / (float) reqWidth); inSampleSize = Math.max(widthRatio, heightRatio); } returninSampleSize; }
/** * 根据计算的inSampleSize，得到压缩后图片 * * @param pathName * @param reqWidth * @param reqHeight * @return */ privateBitmap decodeSampledBitmapFromResource(String pathName, intreqWidth, intreqHeight) { // 第一次解析将inJustDecodeBounds设置为true，来获取图片大小 finalBitmapFactory.Options options = newBitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeFile(pathName, options); // 调用上面定义的方法计算inSampleSize值 options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); // 使用获取到的inSampleSize值再次解析图片 options.inJustDecodeBounds = false; Bitmap bitmap = BitmapFactory.decodeFile(pathName, options);
returnbitmap; }
privateclass ImgBeanHolder { Bitmap bitmap; ImageView imageView; String path; }
privateclass ImageSize { intwidth; intheight; }
/** * 反射获得ImageView设置的最大宽度和高度 * * @param object * @param fieldName * @return */ privatestatic int getImageViewFieldValue(Object object, String fieldName) { intvalue = 0; try{ Field field = ImageView.class.getDeclaredField(fieldName); field.setAccessible(true); intfieldValue = (Integer) field.get(object); if(fieldValue > 0&& fieldValue < Integer.MAX_VALUE) { value = fieldValue; } }catch(Exception e) { } returnvalue; }
} |
使用很简单，如果你在是Adapter中，
| 双击代码复制 | |
| 1 2 3 4 5 | ImageItem item = getItem(position); String path = item.getPath(); ImageView imageView = holder.getImageView(R.id.img_plant); ImageLoader.getInstance().loadImage(path, imageView); imageView.setImageResource(R.drawable.pictures_no); |
更多相关文章
- Android获取图片Uri/path
- 【Android】图片切换组件ImageSwitcher的运用
- Android 创建圆形背景图片
- Android base64 上传图片
- Android显示网络图片相关实现方法浅谈
- android 中Drawable跟Bitmap转换及常用于图片相关操作方法 - And
- android带图片的AlertDialog和文件管理器（代码）
- android GridView实现选中图片放大。