android将bitmap写入缓存，和从缓存中读取

将Bitmap写入缓存可以使用Android的LruCache类或DiskLruCache类。LruCache是一种内存缓存，而DiskLruCache是一种磁盘缓存。

以下是将Bitmap写入LruCache的示例代码：

// 初始化LruCache
int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
int cacheSize = maxMemory / 8;
LruCache<String, Bitmap> memoryCache = new LruCache<String, Bitmap>(cacheSize);

// 写入Bitmap到LruCache
String key = "myBitmapKey";
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.my_bitmap);
memoryCache.put(key, bitmap);

以下是从LruCache中读取Bitmap的示例代码：

// 从LruCache中读取Bitmap
String key = "myBitmapKey";
Bitmap bitmap = memoryCache.get(key);
if (bitmap != null) {
    // 使用Bitmap
} else {
    // LruCache中没有该Bitmap
}

以下是将Bitmap写入DiskLruCache的示例代码：

// 初始化DiskLruCache
File cacheDir = getDiskCacheDir(this, "myCacheDir");
int appVersion = getAppVersion(this);
int valueCount = 1;
long maxSize = 10 * 1024 * 1024; // 10MB
DiskLruCache diskCache = DiskLruCache.open(cacheDir, appVersion, valueCount, maxSize);

// 写入Bitmap到DiskLruCache
String key = "myBitmapKey";
DiskLruCache.Editor editor = diskCache.edit(key);
if (editor != null) {
    OutputStream outputStream = editor.newOutputStream(0);
    Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.my_bitmap);
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream);
    editor.commit();
}

// 关闭DiskLruCache
diskCache.close();

以下是从DiskLruCache中读取Bitmap的示例代码：

// 从DiskLruCache中读取Bitmap
String key = "myBitmapKey";
DiskLruCache.Snapshot snapshot = diskCache.get(key);
if (snapshot != null) {
    InputStream inputStream = snapshot.getInputStream(0);
    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
    // 使用Bitmap
}