Handler倒计时

public class MainActivity extends AppCompatActivity {

    private TextView text_time;
    private Button but_1;
    private int i = 5;
    Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

            if(msg.what==0){
                if (i==0){
                    Intent intent = new Intent(MainActivity.this,Main2Activity.class);
                    startActivity(intent);
                    finish();
                }else{
                    i--;
                    text_time.setText(i+"秒");
                    handler.sendEmptyMessageDelayed(0,1000);
                }

            }

        }
    };
    private SharedPreferences sp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获取控件
        text_time = findViewById(R.id.text_time);
        but_1 = findViewById(R.id.but_1);
        //获取getSharedPreferences
        sp = getSharedPreferences("key",MODE_MULTI_PROCESS);
        //判断
        if(sp.getBoolean("key",false)){

            Intent intent = new Intent(MainActivity.this,Main2Activity.class);
            startActivity(intent);
        }
        //提交
        sp.edit().putBoolean("key",true).commit();
        //点击跳转
        but_1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,Main2Activity.class);
                startActivity(intent);

            }
        });
        //发送消息
        handler.sendEmptyMessageDelayed(0,1000);
    }
}