1 package com.android.utils;  2   3 import java.io.File;  4 import java.io.IOException;  5 import java.io.RandomAccessFile;  6 import java.util.Arrays;  7   8 import android.app.Activity;  9 import android.util.Log; 10  11  12 /** 13  * 在一些对数据实时性要求比较高的场合，如随时可能断电的场合下，同时需要将数据写入文件中， 14  * 这个时候，我们不希望数据在内存中呆太久，最好能够做到同步，这是我们的需求。
 15  * 第一种方案：
 16  *     1. RandomAccessFile
 17  *     2. public RandomAccessFile(File file, String mode) throws FileNotFoundException
 18  *      Constructs a new RandomAccessFile based on file and opens it according to the access string in mode. 
 19  *     3. mode may have one of following values: 
 20  *      1. "r" The file is opened in read-only mode. An IOException is thrown if any of the write methods is called. 
 21  *         2. "rw" The file is opened for reading and writing. If the file does not exist, it will be created. 
 22  *         3. "rws" The file is opened for reading and writing. Every change of the file's content or metadata must be written synchronously to the target device. 
 23  *         4. "rwd" The file is opened for reading and writing. Every change of the file's content must be written synchronously to the target device. 
 24  *     4. 由于我们需要其中的数据同步功能，所以我们选择使用包装RandomAccessFile类，实现要求。
 25  * 第二种方案:
 26  *  1. FileDescriptor中有sync()方法
 27         Ensures that data which is buffered within the underlying implementation is written out to the appropriate device before returning.
 28  *  2. FileOutputStream中的 getFD()方法
 29         Returns a FileDescriptor which represents the lowest level representation of an operating system stream resource. 
 30  *    3. 使用起来感觉没有RandomAccessFile方便，放弃时使用
 31  */ 32  33 public class ZengjfRandomAccessFile { 34     /** 35      * 将整形数组写入文件 36      *  37      * @param filePath         文件路径 38      * @param data             整形数组 39      * @throws IOException 40      */ 41     static public void writeIntArray(String filePath, int[] data) throws IOException { 42         if (null == filePath || null == data)  43             return ; 44          45         if (filePath.trim().equals(""))  46             return ; 47          48         File file = new File(filePath); 49         if (!file.exists())  50             file.createNewFile(); 51              52         if (!file.canWrite())  53             throw new RuntimeException("Zengjf Utils writeIntArray(): no permission for file -- " + filePath + "."); 54          55         // write data 56         RandomAccessFile raf = new RandomAccessFile(file, "rws"); 57         for (int i = 0; i < data.length; i++)  58             raf.writeInt(data[i]); 59          60         raf.close(); 61     } 62  63     /** 64      * 将整形数组写入文件，文件目录被指定，作为使用者可以不用关心 65      *  66      * @param activity         调用这个函数的Activity 67      * @param data             要保存的的整形数组 68      * @throws IOException 69      */ 70     static public void writeIntArray(Activity activity, int[] data) throws IOException { 71         if (null == activity || null == data)  72             return ; 73  74         String filePath = activity.getApplicationContext().getFilesDir().getAbsoluteFile() + "/zengjfData.txt"; 75         writeIntArray(filePath, data); 76     } 77      78     /** 79      * 从文件中读出长度为length的整形数组 80      *  81      * @param filePath        文件路径 82      * @param length          数组长度 83      * @return                返回数组，如果出错，返回null 84      * @throws IOException 85      */ 86     static public int[] readIntArray(String filePath, int length) throws IOException { 87          88         if (null == filePath || length <= 0)  89             return null; 90          91         if (filePath.trim().equals(""))  92             return null; 93          94         File file = new File(filePath);     95         if (!file.canRead())  96             throw new RuntimeException("Zengjf Utils writeIntArray(): no permission for file -- " + filePath + "."); 97  98         int[] data = new int[length];     // for return data 99 100         // if file not exist in first time and file length less than data size, 101         // just create file and make data for it102         if (!file.exists() || (file.length() < (4 * length))) {103             for (int i = 0; i < data.length; i++) 104                 data[i] = 0;105 106             writeIntArray(filePath, data);107             return data;108         }109         110         //get data111         RandomAccessFile raf = new RandomAccessFile(file, "r");112         for (int i = 0; i < length; i++) 113             data[i] = raf.readInt();114         115         raf.close();116         117         return data;118     }119 120     /**121      * 从文件中读取整形数组，文件位置、名已经被指定，作为使用者可以不关心122      * 123      * @param activity        调用这个函数的Activity124      * @param length          数组的长度125      * @return                返回数组，如果出错，返回null126      * @throws IOException127      */128     static public int[] readIntArray(Activity activity, int length) throws IOException {129         if (null == activity || 0 == length) 130             return null;131 132         String filePath = activity.getApplicationContext().getFilesDir().getAbsoluteFile() + "/zengjfData.txt";133         return readIntArray(filePath, length);134     }135     136     /**137      * 往文件中写入原始整形数组，其实就是填充整形0138      * 139      * @param filePath        文件路径140      * @param length          数组大小141      * @throws IOException142      */143     static public void writeRawIntArray(String filePath, int length) throws IOException {144 145         if (null == filePath || length <= 0) 146             return ;147         148         if (filePath.trim().equals("")) 149             return ;150 151         File file = new File(filePath);    152         int[] data = new int[length];     // for return data153 154         // if file not exist in first time, just create file and make data for it155         if (file.exists()) {156             for (int i = 0; i < data.length; i++) 157                 data[i] = 0;158 159             writeIntArray(filePath, data);160         }161     }162     163     /**164      * 165      * 往文件中写入值为0的整形数组，文件位置、名已经被指定，作为使用者可以不关心166      * 167      * @param activity        调用这个函数的Activity168      * @param length          写入数组的长度169      * @throws IOException170      */171     static public void writeRawIntArray(Activity activity, int length) throws IOException{172         if (null == activity || 0 == length) 173             return ;174 175         String filePath = activity.getApplicationContext().getFilesDir().getAbsoluteFile() + "/zengjfData.txt";176         writeRawIntArray(filePath, length);177     }178     179     /**180      * 测试用的的Demo181      * @param activity     调用这个函数的Activity182      */183     static public void testDemo(Activity activity) {184         int[] data = {1, 2, 3, 4, 5, 6};185         try {186             writeIntArray(activity, data);187             int[] redata = readIntArray(activity, 6);188             Log.e("zengjf utils", Arrays.toString(redata));189         } catch (IOException e) {190             // TODO Auto-generated catch block191             e.printStackTrace();192         }193     }194 }