android按行读取文件内容的几个方法
一、简单版
importjava.io.FileInputStream;
voidreadFileOnLine(){
StringstrFileName="Filename.txt";
FileInputStreamfis=openFileInput(strFileName);
StringBuffersBuffer=newStringBuffer();
DataInputStreamdataIO=newDataInputStream(fis);
StringstrLine=null;
while((strLine= dataIO.readLine())!=null){
sBuffer.append(strLine+“\n");
}
dataIO.close();
fis.close();
}
二、简洁版
//读取文本文件中的内容
publicstaticStringReadTxtFile(StringstrFilePath)
{
Stringpath=strFilePath;
Stringcontent="";//文件内容字符串
//打开文件
Filefile=newFile(path);
//如果path是传递过来的参数，可以做一个非目录的判断
if(file.isDirectory())
{
Log.d("TestFile","TheFiledoesn'tnotexist.");
}
else
{
try{
InputStreaminstream=newFileInputStream(file);
if(instream!=null)
{
InputStreamReaderinputreader=newInputStreamReader(instream);
BufferedReaderbuffreader=newBufferedReader(inputreader);
Stringline;
//分行读取
while((line=buffreader.readLine())!=null){
content+=line+"\n";
}
instream.close();
}
}
catch(java.io.FileNotFoundExceptione)
{
Log.d("TestFile","TheFiledoesn'tnotexist.");
}
catch(IOExceptione)
{
Log.d("TestFile",e.getMessage());
}
}
returncontent;
}
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
classWeightRecord{
Stringtimestamp;
floatweight;
publicWeightRecord(Stringtimestamp,floatweight){
this.timestamp=timestamp;
this.weight=weight;
}
}
//开始读取
privateWeightRecord[]readLog()throwsException{
ArrayList<WeightRecord>result=newArrayList<WeightRecord>();
Fileroot=Environment.getExternalStorageDirectory();
if(root==null)
thrownewException("externalstoragedirnotfound");
//首先找到文件
FileweightLogFile=newFile(root,WeightService.LOGFILEPATH);
if(!weightLogFile.exists())
thrownewException("logfile'"+weightLogFile+"'notfound");
if(!weightLogFile.canRead())
thrownewException("logfile'"+weightLogFile+"'notreadable");
longmodtime=weightLogFile.lastModified();
if(modtime==lastRecordFileModtime)
returnlastLog;
//fileexists,isreadable,andisrecentlymodified--rereadit.
lastRecordFileModtime=modtime;
//然后将文件转化成字节流读取
FileReaderreader=newFileReader(weightLogFile);
BufferedReaderin=newBufferedReader(reader);
longcurrentTime=-1;
//逐行读取
Stringline=in.readLine();
while(line!=null){
WeightRecordrec=parseLine(line);
if(rec==null)
Log.e(TAG,"couldnotparseline:'"+line+"'");
elseif(Long.parseLong(rec.timestamp)<currentTime)
Log.e(TAG,"ignoring'"+line+"'sinceit'solderthanprevlogline");
else{
Log.i(TAG,"line="+rec);
result.add(rec);
currentTime=Long.parseLong(rec.timestamp);
}
line=in.readLine();
}
in.close();
lastLog=(WeightRecord[])result.toArray(newWeightRecord[result.size()]);
returnlastLog;
}
//解析每一行
privateWeightRecordparseLine(Stringline){
if(line==null)
returnnull;
String[]split=line.split("[;]");
if(split.length<2)
returnnull;
if(split[0].equals("Date"))
returnnull;
try{
Stringtimestamp=(split[0]);
floatweight= Float.parseFloat(split[1]);
returnnewWeightRecord(timestamp,weight);
}
catch(Exceptione){
Log.e(TAG,"Invalidformatinline'"+line+"'");
returnnull;
}
}
2，保存为文件
publicbooleanlogWeight(IntentbatteryChangeIntent){
Log.i(TAG,"logBattery");
if(batteryChangeIntent==null)
returnfalse;
try{
FileWriterout=null;
if(mWeightLogFile!=null){
try{
out=newFileWriter(mWeightLogFile,true);
}
catch(Exceptione){}
}
if(out==null){
Fileroot=Environment.getExternalStorageDirectory();
if(root==null)
thrownewException("externalstoragedirnotfound");
mWeightLogFile=newFile(root,WeightService.LOGFILEPATH);
booleanfileExists=mWeightLogFile.exists();
if(!fileExists){
if(!mWeightLogFile.getParentFile().mkdirs()){
Toast.makeText(this,"createfilefailed",Toast.LENGTH_SHORT).show();
}
mWeightLogFile.createNewFile();
}
if(!mWeightLogFile.exists()){
Log.i(TAG,"out=null");
thrownewException("creationoffile'"+mWeightLogFile.toString()+"'failed");
}
if(!mWeightLogFile.canWrite())
thrownewException("file'"+mWeightLogFile.toString()+"'isnotwritable");
out=newFileWriter(mWeightLogFile,true);
if(!fileExists){
Stringheader=createHeadLine();
out.write(header);
out.write('\n');
}
}
Log.i(TAG,"out!=null");
Stringextras=createBatteryInfoLine(batteryChangeIntent);
out.write(extras);
out.write('\n');
out.flush();
out.close();
returntrue;
}catch(Exceptione){
Log.e(TAG,e.getMessage(),e);
returnfalse;
}
}