Android 保存数据到SD卡 保存对象（做数据缓存）

public class DataStorageUtils {

    private static final int REQUEST_EXTERNAL_STORAGE = 1;
    private static String[] PERMISSIONS_STORAGE = {
            "android.permission.READ_EXTERNAL_STORAGE",
            "android.permission.WRITE_EXTERNAL_STORAGE" };


    public static void verifyStoragePermissions(Activity activity) {

        try {
            //检测是否有写的权限
            int permission = ActivityCompat.checkSelfPermission(activity,
                    "android.permission.WRITE_EXTERNAL_STORAGE");
            if (permission != PackageManager.PERMISSION_GRANTED) {
                // 没有写的权限，去申请写的权限，会弹出对话框
                ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //判断文件是否存在
    public static boolean fileIsExists(String strFile)
    {
        try
        {
            File f=new File(strFile);
            if(!f.exists())
            {
                return false;
            }

        }
        catch (Exception e)
        {
            return false;
        }

        return true;
    }

    //保存在sd卡
    public static boolean fileSave2SDCard(Object obj) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File sdCardDir = Environment.getExternalStorageDirectory();//获取SDCard目录
            File sdFile = new File(sdCardDir, "obj.out");
            FileOutputStream fos = null;
            ObjectOutputStream oos = null;
            try {
                fos = new FileOutputStream(sdFile);
                oos = new ObjectOutputStream(fos);
                oos.writeObject(obj); //写入
                oos.flush();
                return true;
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fos != null) fos.close();
                    if (oos != null) oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return false;
    }


    //保存在sd卡
    public static boolean fileBean1SDCard(Object obj) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File sdCardDir = Environment.getExternalStorageDirectory();//获取SDCard目录
            File sdFile = new File(sdCardDir, "obj1.out");
            FileOutputStream fos = null;
            ObjectOutputStream oos = null;
            try {
                fos = new FileOutputStream(sdFile);
                oos = new ObjectOutputStream(fos);
                oos.writeObject(obj); //写入
                oos.flush();
                return true;
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fos != null) fos.close();
                    if (oos != null) oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return false;
    }


    //保存在sd卡
    public static boolean fileBean2SDCard(Object obj) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File sdCardDir = Environment.getExternalStorageDirectory();//获取SDCard目录
            File sdFile = new File(sdCardDir, "obj2.out");
            FileOutputStream fos = null;
            ObjectOutputStream oos = null;
            try {
                fos = new FileOutputStream(sdFile);
                oos = new ObjectOutputStream(fos);
                oos.writeObject(obj); //写入
                oos.flush();
                return true;
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fos != null) fos.close();
                    if (oos != null) oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return false;
    }
    //保存在sd卡
    public static boolean fileCardBean(Object obj,String fileName) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File sdCardDir = Environment.getExternalStorageDirectory();//获取SDCard目录
            File sdFile = new File(sdCardDir, fileName+".out");
            FileOutputStream fos = null;
            ObjectOutputStream oos = null;
            try {
                fos = new FileOutputStream(sdFile);
                oos = new ObjectOutputStream(fos);
                oos.writeObject(obj); //写入
                oos.flush();
                return true;
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fos != null) fos.close();
                    if (oos != null) oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return false;
    }


    public static Object readObjFromSDCard(String fileName) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            Object obj;
            File sdCardDir = Environment.getExternalStorageDirectory(); //获取SDCard目录
            //File file = new File(Environment.getExternalStorageDirectory(), "/avator/" + "stf" + myApplication.staffId + System.currentTimeMillis() + ".jpg");
            File sdFile = new File(sdCardDir, fileName + ".out");
            FileInputStream fis = null;
            ObjectInputStream ois = null;
            try {
                fis = new FileInputStream(sdFile); //获得输入流
                ois = new ObjectInputStream(fis);
                obj = ois.readObject();
                return obj;
            } catch (IOException | ClassNotFoundException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fis != null) fis.close();
                    if (ois != null) ois.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

    /**
     * 删除单个文件
     *
     * @param fileName
     *            要删除的文件的文件名
     * @return 单个文件删除成功返回true，否则返回false
     */
    public static boolean deleteFile(String fileName) {
        File file = new File(fileName);
        // 如果文件路径所对应的文件存在，并且是一个文件，则直接删除
        if (file.exists() && file.isFile()) {
            if (file.delete()) {
                System.out.println("删除单个文件" + fileName + "成功！");
                return true;
            } else {
                System.out.println("删除单个文件" + fileName + "失败！");
                return false;
            }
        } else {
            System.out.println("删除单个文件失败：" + fileName + "不存在！");
            return false;
        }
    }

    /**
     * 将String数据存为文件
     */
    public static File wtiteFileFromBytes(String name, String path) {
        byte[] b=name.getBytes();
        BufferedOutputStream stream = null;
        File file = null;
        try {
            file = new File(path);
            FileOutputStream fstream = new FileOutputStream(file);
            stream = new BufferedOutputStream(fstream);
            stream.write(b);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (stream != null) {
                try {
                    stream.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
        }
        return file;
    }

    public static String getFileData(String path){
        StringBuffer buffer = new StringBuffer();
        try {
            FileInputStream fis = new FileInputStream(path);
            InputStreamReader isr = new InputStreamReader(fis,"UTF-8");//文件编码Unicode,UTF-8,ASCII,GB2312,Big5
            Reader in = new BufferedReader(isr);
            int ch;
            while ((ch = in.read()) > -1) {
                buffer.append((char)ch);
            }
            in.close();
        } catch (IOException e) {
            Log.e("yichang","文件不存在!");

        }
        return buffer.toString();  //buffer.toString())就是读出的内容字符
    }
}