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; } }