Android使用自带的程序打开图片或者文本

最近初次接触安卓，正尝试开发云盘，遇到调用本地程序预览图片,文本的问题。查阅相关资料后解决，以记之。

思路：========>>>>使用Android自带的程序打开图片或者文本之类的一些东西，首先需要将数据下载到本地，然后在调用Intent。便可以实现

File file = new File("①");        Intent intent = new Intent(Intent.ACTION_VIEW);        intent.setDataAndType(Uri.fromFile(file), "②");//image/*        startActivity(intent);//此处可能会产生异常（比如说你的MIME类型是打开视频，但是你手机里面没装视频播放器，就会报错）一：    在①处放置的是下载好的文件在手机的存放位置二：   在②处放置的是你需要打开的类型，枚举如下：文件后缀名===MIME类型
                {".3gp"========"video/3gpp"}, 
            {".apk"========"application/vnd.android.package-archive"}, 
            {".asf"========"video/x-ms-asf"}, 
            {".avi"========"video/x-msvideo"}, 
            {".bin"========"application/octet-stream"}, 
            {".bmp"========"image/bmp"}, 
            {".c"========"text/plain"}, 
            {".class"========"application/octet-stream"}, 
            {".conf"========"text/plain"}, 
            {".cpp"========"text/plain"}, 
            {".doc"========"application/msWord"}, 
            {".docx"========"application/vnd.openxmlformats-officedocument.wordPRocessingml.document"}, 
            {".xls"========"application/vnd.ms-Excel"},  
            {".xlsx"========"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"}, 
            {".exe"========"application/octet-stream"}, 
            {".gif"========"image/gif"}, 
            {".gtar"========"application/x-gtar"}, 
            {".gz"========"application/x-gzip"}, 
            {".h"========"text/plain"}, 
            {".htm"========"text/html"}, 
            {".html"========"text/html"}, 
            {".jar"========"application/java-archive"}, 
            {".java"========"text/plain"}, 
            {".jpeg"========"image/jpeg"}, 
            {".jpg"========"image/jpeg"}, 
            {".js"========"application/x-Javascript"}, 
            {".log"========"text/plain"}, 
            {".m3u"========"audio/x-mpegurl"}, 
            {".m4a"========"audio/mp4a-latm"}, 
            {".m4b"========"audio/mp4a-latm"}, 
            {".m4p"========"audio/mp4a-latm"}, 
            {".m4u"========"video/vnd.mpegurl"}, 
            {".m4v"========"video/x-m4v"},  
            {".mov"========"video/quicktime"}, 
            {".mp2"========"audio/x-mpeg"}, 
            {".mp3"========"audio/x-mpeg"}, 
            {".mp4"========"video/mp4"}, 
            {".mpc"========"application/vnd.mpohun.certificate"},        
            {".mpe"========"video/mpeg"},   
            {".mpeg"========"video/mpeg"},   
            {".mpg"========"video/mpeg"},   
            {".mpg4"========"video/mp4"},    
            {".mpga"========"audio/mpeg"}, 
            {".msg"========"application/vnd.ms-Outlook"}, 
            {".ogg"========"audio/ogg"}, 
            {".pdf"========"application/pdf"}, 
            {".png"========"image/png"}, 
            {".pps"========"application/vnd.ms-Powerpoint"}, 
            {".PPT"========"application/vnd.ms-powerpoint"}, 
            {".pptx"========"application/vnd.openxmlformats-officedocument.presentationml.presentation"}, 
            {".prop"========"text/plain"}, 
            {".rc"======== "text/plain"}, 
            {".rmvb"========"audio/x-pn-realaudio"}, 
            {".rtf"======== "application/rtf"}, 
            {".sh"========"text/plain"}, 
            {".tar"========"application/x-tar"},    
            {".tgz"========"application/x-compressed"},  
            {".txt"========"text/plain"}, 
            {".wav"========"audio/x-wav"}, 
            {".wma"========"audio/x-ms-wma"}, 
            {".wmv"========"audio/x-ms-wmv"}, 
            {".wps"========"application/vnd.ms-works"}, 
            {".xml"========"text/plain"}, 
            {".z"========"application/x-compress"}, 
            {".zip"========"application/x-zip-compressed"}, 
            {"", ========"*/*"}