android按行读取文件内容的几个方法

一、简单版

 import java.io.FileInputStream;
 void readFileOnLine(){
     String strFileName = "Filename.txt";
     FileInputStream fis = openFileInput(strFileName);
     StringBuffer sBuffer = new StringBuffer();
     DataInputStream dataIO = new DataInputStream(fis);
     String strLine = null;
     while((strLine =  dataIO.readLine()) != null) {
         sBuffer.append(strLine + “\n");
     }
     dataIO.close();
     fis.close();
 }

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

 //首先定义一个数据类型，用于保存读取文件的内容
 class WeightRecord {
         String timestamp;
         float weight;
         public WeightRecord(String timestamp, float weight) {
             this.timestamp = timestamp;
             this.weight = weight;

         }
     }

 //开始读取
  private WeightRecord[] readLog() throws Exception {
         ArrayList<WeightRecord> result = new ArrayList<WeightRecord>();
         File root = Environment.getExternalStorageDirectory();
         if (root == null)
             throw new Exception("external storage dir not found");
         //首先找到文件
         File weightLogFile = new File(root,WeightService.LOGFILEPATH);
         if (!weightLogFile.exists())
             throw new Exception("logfile '"+weightLogFile+"' not found");
         if (!weightLogFile.canRead())
             throw new Exception("logfile '"+weightLogFile+"' not readable");
         long modtime = weightLogFile.lastModified();
         if (modtime == lastRecordFileModtime)
             return lastLog;
         // file exists, is readable, and is recently modified -- reread it.
         lastRecordFileModtime = modtime;
         // 然后将文件转化成字节流读取
         FileReader reader = new FileReader(weightLogFile);
         BufferedReader in = new BufferedReader(reader);
         long currentTime = -1;
         //逐行读取
         String line = in.readLine();
         while (line != null) {
             WeightRecord rec = parseLine(line);
             if (rec == null)
                 Log.e(TAG, "could not parse line: '"+line+"'");
             else if (Long.parseLong(rec.timestamp) < currentTime)
                 Log.e(TAG, "ignoring '"+line+"' since it's older than prev log line");
             else {
                 Log.i(TAG,"line="+rec);
                 result.add(rec);
                 currentTime = Long.parseLong(rec.timestamp);
             }
             line = in.readLine();
         }
         in.close();
         lastLog = (WeightRecord[]) result.toArray(new WeightRecord[result.size()]);
         return lastLog;
     }
     //解析每一行
     private WeightRecord parseLine(String line) {
         if (line == null)
             return null;
         String[] split = line.split("[;]");
         if (split.length < 2)
             return null;
         if (split[0].equals("Date"))
             return null;
         try {
             String timestamp =(split[0]);
             float weight =  Float.parseFloat(split[1]) ;
             return new WeightRecord(timestamp,weight);
         }
         catch (Exception e) {
             Log.e(TAG,"Invalid format in line '"+line+"'");
             return null;
         }
     }

2，保存为文件

 public boolean logWeight(Intent batteryChangeIntent) {
             Log.i(TAG, "logBattery");
             if (batteryChangeIntent == null)
                 return false;
             try {
                 FileWriter out = null;
                 if (mWeightLogFile != null) {
                     try {
                         out = new FileWriter(mWeightLogFile, true);
                     }
                     catch (Exception e) {}
                 }
                 if (out == null) {
                     File root = Environment.getExternalStorageDirectory();
                     if (root == null)
                         throw new Exception("external storage dir not found");
                     mWeightLogFile = new File(root,WeightService.LOGFILEPATH);
                     boolean fileExists = mWeightLogFile.exists();
                     if (!fileExists) {
                         if(!mWeightLogFile.getParentFile().mkdirs()){
                             Toast.makeText(this, "create file failed", Toast.LENGTH_SHORT).show();
                         }
                         mWeightLogFile.createNewFile();
                     }
                     if (!mWeightLogFile.exists()) {
                         Log.i(TAG, "out = null");
                         throw new Exception("creation of file '"+mWeightLogFile.toString()+"' failed");
                     }
                     if (!mWeightLogFile.canWrite())
                         throw new Exception("file '"+mWeightLogFile.toString()+"' is not writable");
                     out = new FileWriter(mWeightLogFile, true);
                     if (!fileExists) {
                         String header = createHeadLine();
                         out.write(header);
                         out.write('\n');
                     }
                 }
                 Log.i(TAG, "out != null");
                 String extras = createBatteryInfoLine(batteryChangeIntent);
                 out.write(extras);
                 out.write('\n');
                 out.flush();
                 out.close();
                 return true;
             } catch (Exception e) {
                 Log.e(TAG,e.getMessage(),e);
                 return false;
             }
         }