高效显示Bitmap

This class covers some common techniques for processing and loading Bitmap objects in a way that keeps your user interface (UI) components responsive and avoids exceeding your application memory limit. If you're not careful, bitmaps can quickly consume your available memory budget leading to an application crash due to the dreaded exception:
java.lang.OutofMemoryError: bitmap size exceeds VM budget.

There are a number of reasons why loading bitmaps in your Android application is tricky:

• Mobile devices typically have constrained system resources. Android devices can have as little as 16MB of memory available to a single application. The Android Compatibility Definition Document (CDD), Section 3.7. Virtual Machine Compatibility gives the required minimum application memory for various screen sizes and densities. Applications should be optimized to perform under this minimum memory limit. However, keep in mind many devices are configured with higher limits.
• Bitmaps take up a lot of memory, especially for rich images like photographs. For example, the camera on the Galaxy Nexus takes photos up to 2592x1936 pixels (5 megapixels). If the bitmap configuration used is ARGB_8888 (the default from the Android 2.3 onward) then loading this image into memory takes about 19MB of memory (2592*1936*4 bytes), immediately exhausting the per-app limit on some devices.
• Android app UI’s frequently require several bitmaps to be loaded at once. Components such as ListView, GridView and ViewPager commonly include multiple bitmaps on-screen at once with many more potentially off-screen ready to show at the flick of a finger.

Lessons

高效加载较大的 Bitmaps

This lesson walks you through decoding large bitmaps without exceeding the per application memory limit.

UI线程外处理Bitmap

Bitmap processing (resizing, downloading from a remote source, etc.) should never take place on the main UI thread. This lesson walks you through processing bitmaps in a background thread using AsyncTask and explains how to handle concurrency issues.

缓存Bitmap

This lesson walks you through using a memory and disk bitmap cache to improve the responsiveness and fluidity of your UI when loading multiple bitmaps.

在UI中显示Bitmap

This lesson brings everything together, showing you how to load multiple bitmaps into components like ViewPager and GridView using a background thread and bitmap cache.