public class Welcome extends Activity {  private final long SPLASH_LENGTH = 2000;  Handler handler = new Handler();  public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.farst_img);        //定義一個setting記錄APP是幾次啟動?。?！    SharedPreferences setting = getSharedPreferences("com.example.hr_jie", 0);    Boolean user_first = setting.getBoolean("FIRST", true);    if (user_first) {// 第一次則跳轉到歡迎頁面      setting.edit().putBoolean("FIRST", false).commit();      tiaozhuanzhu();    } else {//如果是第二次啟動則直接跳轉到主頁面      tiaozhuanfu();    }  }    public void tiaozhuanzhu(){   handler.postDelayed(new Runnable() { //使用handler的postDelayed實現延時跳轉            public void run() {          Intent intent = new Intent(Welcome.this, Welcome_four.class);          startActivity(intent);          finish();          }      }, SPLASH_LENGTH);//2秒后跳轉至應用主界面MainActivity }    public void tiaozhuanfu(){   handler.postDelayed(new Runnable() {//使用handler的postDelayed實現延時跳轉            public void run() {          Intent intent = new Intent(Welcome.this, MainActivity.class);          startActivity(intent);          finish();          }      }, SPLASH_LENGTH);//2秒后跳轉至應用歡迎界面}}