倒计时

public class MainActivity extends AppCompatActivity {    private Handler handler=new Handler();    private SharedPreferences sharedPreferences;    private SharedPreferences.Editor editor;    private boolean First;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        sharedPreferences=getSharedPreferences("First",MODE_PRIVATE);        First=sharedPreferences.getBoolean("First",true);        if(First) {            handler.postDelayed(new Runnable() {                @Override                public void run() {                    Intent intent = new Intent(MainActivity.this, Main2Activity.class);                    startActivity(intent);                }            }, 2000);        }else {            Intent intent = new Intent(MainActivity.this, Main2Activity.class);            startActivity(intent);        }        editor = sharedPreferences.edit();        editor.putBoolean("First",false);        editor.commit();    }}<---------------------------------------------------------------------------------------------->
public class Main2Activity extends AppCompatActivity {    private TextView textView;    private int time = 5;    private Handler handler = new Handler();    private Runnable runnable = new Runnable() {        @Override        public void run() {            time--;            handler.postDelayed(this, 1000);            textView.setText("跳转" + time + "秒");            if (time == 0) {                Intent intent = new Intent(Main2Activity.this, Main3Activity.class);                startActivity(intent);                finish();            } else {                textView.setOnClickListener(new View.OnClickListener() {                    @Override                    public void onClick(View view) {                        Intent intent = new Intent(Main2Activity.this, Main3Activity.class);                        startActivity(intent);                        handler.removeCallbacks(runnable);                        finish();                    }                });            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main2);        textView = (TextView) findViewById(R.id.t1);        handler.postDelayed(runnable, 0);    }}