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public class MainActivity   extends AppCompatActivity   {

    private Button dialog1,dialog2;

    private AlertDialog alert;

    private Timer timerl;

    private MyHandler handler;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        timerl=new Timer();

        handler=new MyHandler();

        dialog1=(Button)findViewById(R.id.dialog1);

        dialog1.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View view) {

                showAlertDialog();

            }

        });

    }

    private void showAlertDialog(){

        AlertDialog.Builder   builder=new AlertDialog(this);

        builder.setTitle("confirm!");

        builder.setMessage("welcome   to use~");

        builder.setCancelable(false);

        alert=builder.create();

        alert.show();

        timerl.schedule(new CloseDialogTask(),4000);

    }

    private class CloseDialogTask extends TimerTask

    {

     private void run(){

         handler.sendEmptyMessage(0);

     }    

    }

    private class MyHandler extends Handler{

        public void handleMessage(Message msg){

            alert.dismiss();

        }

    }