一、保存文件到手机内存
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/** * 保存数据到手机rom的文件里面. * @param context 应用程序的上下文 提供环境 * @param name 用户名 * @param password 密码 * @throws exception */public static void savetorom(context context, string name , string password) throws exception{ //file file = new file("/data/data/com.itheima.login/files/info.txt"); file file = new file(context.getfilesdir(),"info.txt");//该文件在data下的files文件夹下getcachedir()在cache文件夹下 文件大小不要超过1mb fileoutputstream fos = new fileoutputstream(file); string txt = name+":"+password; fos.write(txt.getbytes()); fos.flush(); fos.close(); } |
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/** * 获取保存的数据 * @param context * @return */public static map<string,string> getuserinfo(context context) { file file = new file(context.getfilesdir(),"info.txt"); try { fileinputstream fis = new fileinputstream(file); //也可直接读取文件string result = streamtools.readfromstream(fis); bufferedreader br = new bufferedreader(new inputstreamreader(fis)); string str = br.readline(); string[] infos = str.split(":"); map<string,string> map = new hashmap<string, string>(); map.put("username", infos[0]); map.put("password", infos[1]); return map; } catch(exception e) { e.printstacktrace(); return null; } }//最后可以直接调用上面的方法读取信息map<string, string> map = getuserinfo(this);if(map!=null){textview.settext(map.get(“username”));} |
二、保存文件到sd卡
获取手机sd空间的大小：
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file path = environment.getexternalstoragedirectory(); statfs stat = new statfs(path.getpath()); long blocksize = stat.getblocksize(); long totalblocks = stat.getblockcount(); long availableblocks = stat.getavailableblocks(); long totalsize = blocksize*totalblocks; long availsize = blocksize * availableblocks; string totalstr = formatter.formatfilesize(this,totalsize); string availstr = formatter.formatfilesize(this, availsize); tv.settext("总空间"+totalstr+"\n"+"可用空间"+availstr); |
加入写外部存储的权限：
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<uses-permission android:name="android.permission.write_external_storage"/>public static void save(string name ,string password) throws exception{if (environment.getexternalstoragestate().equals(environment.media_mounted)){file file = new file(environment.getexternalstoragedirectory(),"info.txt");//也可直接写/sdcard/info.txt 先判断sd卡是否存在 fileoutputstream fos = new fileoutputstream(file); string txt = name+":"+password; fos.write(txt.getbytes()); fos.flush(); fos.close();// 使用randomaccessfile像文件追加内容fileoutputstream会把原有的文件内容清空//randomaccessfile raf = new randomaccessfile(file,"rw");//raf.seek(file.length()); 将文件指针移动到最后//raf.write(name.getbytes()+password.getbytes());//raf.close(); }} |
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//读取文件 加入读取权限public static string read(){ try { if (environment.getexternalstoragestate().equals(environment.media_mounted)){ file sdcarddir = environment.getexternalstoragedirectory(); fileinputstream fis = new fileinputstream(sdcarddir.getcanonicalpath() + "info.txt"); bufferedreader br = new bufferedreader(new inputstreamreader(fis)); stringbuilder sb = new stringbuilder(""); string line = null; while ((line = br.readline())!= null){ sb.append(line); } return sb.tostring(); } } catch (exception e) { e.printstacktrace(); } return null; } |
三、sharedpreferences的使用
sharedpreference是开发中常用的一种存储方式，主要存储一些系统不变的参数如是否是第一次进入应用程序等，通过键值对的方式进行存储
可以存储的类型：booleans, floats, ints, longs,strings.
getsharedpreferences() - 存储多个参数
getpreferences() - 仅存储一个参数并且不需要指定名字（key）
写入的步骤：
sharedpreferences调用edit（）得到一个editor对象
使用 putboolean() and putstring()添加值
提交事务完成存储
读取时：只需要调用sharedpreferences的getboolean() and getstring()
下面是示例代码：
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public class mysharedpreference { private context context; private sharedpreferences sp ; private editor edit; public mysharedpreference(context context){ this.context = context; } public boolean savemessage(string name,string pwd){ boolean flag = false; sp = context.getsharedpreferences("userinfo",context.mode_private); //mode定义了访问的权限现在是本应用可以访问 edit = sp.edit(); edit.putstring("name", name); edit.putstring("pwd", pwd); flag = edit.commit();//提交事务将数据持久化到存储器中 return flag; } public map<string,object> getmessage(){ map<string,object> map = new hashmap<string, object>(); sp = context.getsharedpreferences("userinfo", context.mode_private); string name = sp.getstring("name", ""); string pwd = sp.getstring("pwd", ""); map.put("name", name); map.put("pwd",pwd); return map; }} |
