1.cache Image in memory, disk
2.get Image in another thread
1.last view error when nfc launch app, fix it
1.process bar listen back key
2.app crash when sd card cannot be written,fix it but not perfect
1.async task make app crash sometimes, fix it
2.display err image in list view sometimes, fix it
Merge pull request #10 from dengquan/master

get image in async tast and cache it