一、保存文件到手机内存
/**
* 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();
}
/**
* 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：
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：
<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();
}
}
//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：
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;
}
}
