java.lang.NullPointerException at com.example.andre.gastoscaminhao.GastosActivity$1.onClick(GastosActivity.java:31)

adicionarGasto.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
linha 31        if (TextUtils.isEmpty(valorDespesa.getText())) {
                    Toast.makeText(GastosActivity.this, "Adicione um valor", Toast.LENGTH_SHORT).show();
                } else {
                    startActivity(new Intent(GastosActivity.this, TelaInicial.class));
                }
            }
        });