Android应用中怎么将文字逐字显示

public static void startTv(final int n) {  new Thread(      new Runnable() {        @Override        public void run() {          try {            final String stv = s.substring(0, n);//截取要填充的字符串            tv.post(new Runnable() {              @Override              public void run() {                tv.setText(stv);              }            });            Thread.sleep(time);//休息片刻            nn = n + 1;//n+1；多截取一个            if (nn <= length) {//如果还有汉字，那么继续开启线程，相当于递归的感觉              startTv(nn);            }          } catch (InterruptedException e) {            e.printStackTrace();          }        }      }  ).start();}