public void showKeyboard() { 
    if(editText!=null){ 
      //设置可获得焦点 
      editText.setFocusable(true); 
      editText.setFocusableInTouchMode(true); 
      //请求获得焦点 
      editText.requestFocus(); 
      //调用系统输入法 
      InputMethodManager inputManager = (InputMethodManager) editText 
          .getContext().getSystemService(Context.INPUT_METHOD_SERVICE); 
      inputManager.showSoftInput(editText, 0); 
    } 
}

dialog.show(); 
Timer timer = new Timer(); 
timer.schedule(new TimerTask() { 
  
  @Override 
  public void run() { 
    dialog.showKeyboard(); 
  } 
}, 200);