android按行读取文件内容的几个方法

一、简单版

 1 import java.io.FileInputStream;

 2 void readFileOnLine(){

 3     String strFileName = "Filename.txt";

 4     FileInputStream fis = openFileInput(strFileName);

 5     StringBuffer sBuffer = new StringBuffer();

 6     DataInputStream dataIO = new DataInputStream(fis);

 7     String strLine = null;

 8     while((strLine =  dataIO.readLine()) != null) {

 9         sBuffer.append(strLine + “\n");

10     }

11     dataIO.close();

12     fis.close();

13 }

 二、简洁版

public static String ReadTxtFile(String strFilePath)

    {

            String path = strFilePath;

            String content = "";     //文件内容字符串

            File file = new File(path);    //打开文件

            

            if (file.isDirectory())    //如果path是传递过来的参数，可以做一个非目录的判断

            {

                Log.d("TestFile", "The File doesn't not exist.");

            }

            else

            {

                try {

                    InputStream instream = new FileInputStream(file); 

                    if (instream != null) 

                    {

                        InputStreamReader inputreader = new InputStreamReader(instream);

                        BufferedReader buffreader = new BufferedReader(inputreader);

                        String line;

                        //分行读取

                        while (( line = buffreader.readLine()) != null) {

                            content += line + "\n";

                        }                

                        instream.close();

                    }

                }

                catch (java.io.FileNotFoundException e) 

                {

                    Log.d("TestFile", "The File doesn't not exist.");

                } 

                catch (IOException e) 

                {

                     Log.d("TestFile", e.getMessage());

                }

            }

            return content;

    }

 三、用于长时间使用的apk，并且有规律性的数据

1，逐行读取文件内容

 1 //首先定义一个数据类型，用于保存读取文件的内容 

 2 class WeightRecord {

 3         String timestamp;

 4         float weight;

 5         public WeightRecord(String timestamp, float weight) {

 6             this.timestamp = timestamp;

 7             this.weight = weight;

 8             

 9         }

10     }

11     

12 //开始读取

13  private WeightRecord[] readLog() throws Exception {

14         ArrayList<WeightRecord> result = new ArrayList<WeightRecord>();

15         File root = Environment.getExternalStorageDirectory();

16         if (root == null)

17             throw new Exception("external storage dir not found");

18         //首先找到文件

19         File weightLogFile = new File(root,WeightService.LOGFILEPATH);

20         if (!weightLogFile.exists())

21             throw new Exception("logfile '"+weightLogFile+"' not found");

22         if (!weightLogFile.canRead())

23             throw new Exception("logfile '"+weightLogFile+"' not readable");

24         long modtime = weightLogFile.lastModified();

25         if (modtime == lastRecordFileModtime)

26             return lastLog;

27         // file exists, is readable, and is recently modified -- reread it.

28         lastRecordFileModtime = modtime;

29         // 然后将文件转化成字节流读取

30         FileReader reader = new FileReader(weightLogFile);

31         BufferedReader in = new BufferedReader(reader);

32         long currentTime = -1;

33         //逐行读取

34         String line = in.readLine();

35         while (line != null) {

36             WeightRecord rec = parseLine(line);

37             if (rec == null)

38                 Log.e(TAG, "could not parse line: '"+line+"'");

39             else if (Long.parseLong(rec.timestamp) < currentTime)

40                 Log.e(TAG, "ignoring '"+line+"' since it's older than prev log line");

41             else {

42                 Log.i(TAG,"line="+rec);

43                 result.add(rec);

44                 currentTime = Long.parseLong(rec.timestamp);

45             }

46             line = in.readLine();

47         }

48         in.close();

49         lastLog = (WeightRecord[]) result.toArray(new WeightRecord[result.size()]);

50         return lastLog;

51     }

52     //解析每一行

53     private WeightRecord parseLine(String line) {

54         if (line == null)

55             return null;

56         String[] split = line.split("[;]");

57         if (split.length < 2)

58             return null;

59         if (split[0].equals("Date"))

60             return null;

61         try {

62             String timestamp =(split[0]);

63             float weight =  Float.parseFloat(split[1]) ;

64             return new WeightRecord(timestamp,weight);

65         }

66         catch (Exception e) {

67             Log.e(TAG,"Invalid format in line '"+line+"'");

68             return null;

69         }

70     }

 2，保存为文件

 1 public boolean logWeight(Intent batteryChangeIntent) {

 2             Log.i(TAG, "logBattery");

 3             if (batteryChangeIntent == null)

 4                 return false;

 5             try {

 6                 FileWriter out = null;

 7                 if (mWeightLogFile != null) {

 8                     try {

 9                         out = new FileWriter(mWeightLogFile, true);

10                     }

11                     catch (Exception e) {}

12                 }

13                 if (out == null) {

14                     File root = Environment.getExternalStorageDirectory();

15                     if (root == null)

16                         throw new Exception("external storage dir not found");

17                     mWeightLogFile = new File(root,WeightService.LOGFILEPATH);

18                     boolean fileExists = mWeightLogFile.exists();

19                     if (!fileExists) {

20                         if(!mWeightLogFile.getParentFile().mkdirs()){

21                             Toast.makeText(this, "create file failed", Toast.LENGTH_SHORT).show();

22                         }

23                         mWeightLogFile.createNewFile();

24                     }

25                     if (!mWeightLogFile.exists()) {

26                         Log.i(TAG, "out = null");

27                         throw new Exception("creation of file '"+mWeightLogFile.toString()+"' failed");

28                     }

29                     if (!mWeightLogFile.canWrite()) 

30                         throw new Exception("file '"+mWeightLogFile.toString()+"' is not writable");

31                     out = new FileWriter(mWeightLogFile, true);

32                     if (!fileExists) {

33                         String header = createHeadLine();

34                         out.write(header);

35                         out.write('\n');

36                     }

37                 }

38                 Log.i(TAG, "out != null");

39                 String extras = createBatteryInfoLine(batteryChangeIntent);

40                 out.write(extras);

41                 out.write('\n');

42                 out.flush();

43                 out.close();

44                 return true;

45             } catch (Exception e) {

46                 Log.e(TAG,e.getMessage(),e);

47                 return false;

48             }

49         }