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”));
}
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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);
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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;
}
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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;
}
}
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