Thanks Sachin,
Actually i am scrolling top to bottom. it's working but i am not able to click on element in a list .
public void swipe_vertical() throws InterruptedException{
Dimension size = driver.manage().window().getSize();
int height = size.height;
int width = size.width;
System.out.println("height=" +size.height+"width="+size.width);
int startx = size.width/2;
int endx = size.width/2;
int starty = size.height - size.height/4;
//int starty = size.height - size.height/6;
//int starty = size.height - size.height/8;
int endy = size.height/4;
System.out.println("vertical swipe");
driver.swipe(startx,starty,endx,endy,200);
Thread.sleep(10000);
and
///List <WebElement> element = driver.findElementsByClassName("android.widget.LinearLayout");
//for (int i=1;i<=element.size();i++){
//if(!element.get(i).isDisplayed()){
//driver.swipe(startx, starty, endx, endy, 200);
//}
using this i am not able to click on a element.