How to add data to an existing .txt file in android -

i developing application reads data coming accelerometer , want save them in .txt file, can later process them.

so far have been able readings , save 1 reading, understand create new file overwrites existing file. want have measurements moment push start button, until push stop button.

here code i'm using:

public class mainactivity extends appcompatactivity implements sensoreventlistener, view.onclicklistener {  private sensormanager msensormanager;  private sensor maccelerometer; private button bstart, bstop; float[] acceleration = new float[3]; private string mstring;  myfile file = new myfile(this);   @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      bstart = (button)findviewbyid(r.id.start);     bstop = (button)findviewbyid(r.id.stop);      msensormanager=(sensormanager)getsystemservice(sensor_service);     maccelerometer = msensormanager.getdefaultsensor(sensor.type_accelerometer);      bstart.setonclicklistener(this);     bstop.setonclicklistener(this);     bstart.setenabled(true);     bstop.setenabled(false); }  @override public void onaccuracychanged(sensor sensor, int accuracy) {}  public final void onsensorchanged(sensorevent event){     if(event.sensor.gettype() ==  sensor.type_accelerometer){         acceleration[0] = event.values[0];         acceleration[1] = event.values[1];         acceleration[2] = event.values[2];         textview mtextview1 = (textview) findviewbyid(r.id.textview1);         textview mtextview2 = (textview) findviewbyid(r.id.textview2);         textview mtextview3 = (textview) findviewbyid(r.id.textview3);         mtextview1.settext("x:"+string.valueof( acceleration[0]));         mtextview2.settext("y:"+string.valueof( acceleration[1]));         mtextview3.settext("z:"+string.valueof( acceleration[2]));          file.writetosd(acceleration[0] + "," +acceleration[1] + "," +acceleration[2] + "\n");     } }  @override public void onclick(view v) {     switch(v.getid()){         case r.id.start:             bstart.setenabled(false);             bstop.setenabled(true);             msensormanager.registerlistener(this, maccelerometer, sensormanager.sensor_delay_normal);             break;         case r.id.stop:             bstart.setenabled(true);             bstop.setenabled(false);             msensormanager.unregisterlistener(this);             break;     } } 

}

and myfile class, job gets done following:

public class myfile {  string tag = "myfile"; context context;  public myfile(context context) {     this.context = context; }  public boolean writetosd(string text) {     boolean write_successful = false;     file root = null;     try {         // check sdcard         root = environment.getexternalstoragedirectory();         log.i(tag, "path.." + root.getabsolutepath());          //check sdcard permission         if (root.canwrite()) {             file filedir = new file(root.getabsolutepath());             filedir.mkdirs();              file file = new file(filedir, "samplefile.txt");             filewriter filewriter = new filewriter(file);             bufferedwriter out = new bufferedwriter(filewriter);             out.append(text);             out.flush();             out.close();             write_successful = true;         }     } catch (ioexception e) {        e.printstacktrace();         write_successful = false;     }     return write_successful; } 

}

another question have why can not store .txt file in sdcard , saved in internal memory.

thank time , help

try code. set second argument of filewriter true. can append existing file

 file file = new file("hello.txt");      file.createnewfile();      filewriter writer = new filewriter(file,true);   writer.write("writes content file");   writer.flush();  writer.close();