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         }

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