android问题说难不难，说简单不简单

一共有4个activity功能都已实现 可是问题如下：第一个跳第二的时候跳不过去  直接就跳到第4页面当我从第4页面想返回到第二页面的时候  确先跳到3  然后在跳到2！代码没问题
触发事件代码：
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        switch (position) {
            case 0:
                Intent intent = new Intent();
                intent.setClass(Glaciter.this, Island.class);
                startActivity(intent);
               
                
            case 1:
                Intent xiintent =new Intent();
                xiintent.setClass(Glaciter.this,xizangjieshao.class);
                //xiintent.setClass(Glaciter.this,)
                startActivity(xinintent);
                
                
            case 2:
               Intent xinintent =new Intent();
               xinintent.setClass(Glaciter.this, xinxilanjieshao.class);
               startActivity(xinintent);
               
               
            case 3:
            Intent heiintent=new Intent();
            heiintent.setClass(Glaciter.this, heishuixianjieshao.class);
            startActivity(heiintent);
           
            
                
        }        // TODO Auto-generated method stub    }返回代码：   public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
            Intent intent = new Intent(Island.this, Glaciter.class);
            //startActivity(intent);
            setResult(RESULT_OK, intent);
            finish();
            overridePendingTransition(R.anim.slide_up_in, R.anim.slide_down_out);
            return false;        }        return false;    }