How i can get .txt file read line by line - character

Question

I have a file on the SDcard - "file.txt" containing telephone numbers in separate line.
I want to display line first, and then if I press a button, the second line should be displayed in the TextView and the first line should disappear.
I have code that simply reads the contents of txt file and fully insert all rows in TextView:
How should I change this code to the serial output the following line when you press the button????
File sdcard = Environment.getExternalStorageDirectory();
File file = new File(sdcard,"file.txt");
StringBuilder text = new StringBuilder();
try {
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
line = br.readLine();
text.append(line);
text.append('\n');
}
}
catch (IOException e) {
}
tv.setText(text);
How should I change this code to the serial output the following line when you press the button????

Answer 1

You could store the content of the file in ArrayList< String> , and then, upon pressing a button, change the text in your TextView to another in the list. Something like:
Reading file and storing in a list:
//make this a class member variable
List<String> numbers = new ArrayList<String>();
while((line = br.readLine()) != null) {
//store each line in our list as separate entry
numbers.add(line);
}
Updating TextView upon button press:
//make this a class member variable
//this is being used to get the line from list
int currentLine = 0;
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//set the text
tv.setText(numbers.get(currentLine));
//increment currentLine
currentLine++;
//make sure we don't go beyond the number of lines stored in the list
//so if we reach the last index, we start from the beginning
if (currentLine == numbers.size()) {
currentLine = 0;
}
}
});